Marsh & McLennan Companies 10-K 2023-12-31

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31, 2023

OR

Commission File No. 1-5998

Marsh & McLennan Companies, Inc.

(Exact name of registrant as specified in its charter)

1166 Avenue of the Americas

New York, New York 10036-2774

(Address of principal executive offices; Zip Code)

(212) 345-5000

Registrant’s telephone number, including area code

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ý No ¨

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes ¨ No ý

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ý No ¨

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ý No ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a smaller reporting Company. See the definitions of "large accelerated filer," "accelerated filer" and "smaller reporting Company" in Rule 12b-2 of the Exchange Act. (Check one):

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant is a shell Company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ý

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. Yes ☒ No ¨

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ¨

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive- based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b). ¨

As of June 30, 2023, the aggregate market value of the registrant's common stock held by non-affiliates of the registrant was approximately $92,849,878,606 computed by reference to the closing price of such stock as reported on the New York Stock Exchange on June 30, 2023.

As of February 8, 2024, there were outstanding 491,656,196 shares of common stock, par value $1.00 per share, of the registrant.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of Marsh & McLennan Companies, Inc.’s Notice of Annual Meeting and Proxy Statement for the 2024 Annual Meeting of Stockholders (the "2024 Proxy Statement") are incorporated by reference in Part III of this Form 10-K.

INFORMATION CONCERNING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K contains "forward-looking statements," as defined in the Private Securities Litigation Reform Act of 1995. These statements, which express management's current views concerning future events or results, use words like "anticipate," "assume," "believe," "continue," "estimate," "expect," "intend," "plan," "project" and similar terms, and future or conditional tense verbs like "could," "may," "might," "should," "will" and "would".

Forward-looking statements are subject to inherent risks and uncertainties that could cause actual results to differ materially from those expressed or implied in our forward-looking statements. Factors that could materially affect our future results include, among other things:

• the impact of geopolitical or macroeconomic conditions on us, our clients and the countries and industries in which we operate, including from multiple major wars, escalating conflict throughout the Middle East and rising tension in the South China Sea, slower GDP growth or recession, lower interest rates, capital markets volatility and inflation;

• the impact from lawsuits or investigations arising from errors and omissions, breaches of fiduciary duty or other claims against us in our capacity as a broker or investment advisor, including claims related to our investment business’ ability to execute timely trades;

• the increasing prevalence of ransomware, supply chain and other forms of cyberattacks, and their potential to disrupt our operations or the operations of our third party vendors, and result in the disclosure of confidential client or company information;

• the financial and operational impact of complying with laws and regulations, including domestic and international sanctions regimes, anti-corruption laws such as the U.S. Foreign Corrupt Practices Act, U.K. Anti Bribery Act and cybersecurity, data privacy and artificial intelligence regulations;

• our ability to attract, retain and develop industry leading talent;

• our ability to compete effectively and adapt to competitive pressures in each of our businesses, including from disintermediation as well as technological change, digital disruption and other types of innovation such as artificial intelligence;

• our ability to manage potential conflicts of interest, including where our services to a client conflict, or are perceived to conflict, with the interests of another client or our own interests;

• the impact of changes in tax laws, guidance and interpretations, such as the implementation of the Organization for Economic Cooperation and Development international tax framework, or the increasing number of disagreements with and challenges by tax authorities in the current global tax environment; and

• the regulatory, contractual and reputational risks that arise based on insurance placement activities and insurer revenue streams.

The factors identified above are not exhaustive. Further information concerning Marsh McLennan and its businesses, including information about factors that could materially affect our results of operations and financial condition, is contained in the Company's filings with the Securities and Exchange Commission, including the "Risk Factors" section in Part I, Item 1A of this report and the "Management’s Discussion and Analysis of Financial Condition and Results of Operations" section in Part II, Item 7 of this report. Marsh McLennan and its subsidiaries operate in a dynamic business environment in which new risks emerge frequently. Accordingly, we caution readers not to place undue reliance on any forward-looking statements, which are based only on information currently available to us and speak only as of the dates on which they are made. The Company undertakes no obligation to update or revise any forward-looking statement to reflect events or circumstances arising after the date on which it is made.

i

TABLE OF CONTENTS

ii

PART I

References in this report to "we", "us" and "our" are to Marsh & McLennan Companies, Inc. and its consolidated subsidiaries (the "Company" or "Marsh McLennan"), unless the context otherwise requires.

GENERAL

Marsh McLennan is the world's leading professional services firm in the areas of risk, strategy and people. We help clients build the confidence to thrive through the power of perspective of our four market-leading businesses. With annual revenue of $23 billion, we have more than 85,000 colleagues advising clients in over 130 countries.

Marsh provides data-driven risk advisory services and insurance solutions to commercial and consumer clients. Guy Carpenter develops advanced risk, reinsurance and capital strategies that help clients grow profitably and pursue emerging opportunities. Mercer delivers advice and technology-driven solutions that help organizations redefine the world of work, reshape retirement and investment outcomes, and unlock health and well-being for a changing workforce. Oliver Wyman Group serves as a critical strategic, economic and brand advisor to private sector and governmental clients. Our four businesses also collaborate together to deliver new solutions to help clients manage complex and interconnected risks.

The Company conducts business through two segments:

• Risk and Insurance Services** includes risk management activities (risk advice, risk transfer and risk control and mitigation solutions) as well as insurance and reinsurance broking and services. The Company conducts business in this segment through Marsh and Guy Carpenter.

• Consulting** includes health, wealth and career advice, solutions and products, and specialized management, strategic, economic and brand consulting services. The Company conducts business in this segment through Mercer and Oliver Wyman Group.

We describe our current segments in further detail below. We provide financial information about our segments in our consolidated financial statements included under Part II, Item 8 of this report.

OUR BUSINESSES

RISK AND INSURANCE SERVICES

The Risk and Insurance Services segment generated approximately 62% of the Company's total revenue in 2023 and employs approximately 49,300 colleagues worldwide. The Company conducts business in this segment through Marsh and Guy Carpenter.

MARSH

Marsh is the world's leading insurance broker and risk advisor, serving companies, institutions and individuals. From its founding in 1871 to the present day, Marsh has demonstrated a commitment to thought leadership, innovation and insurance expertise to meet its clients’ needs. Marsh’s pioneering contributions include introducing the practice of client representation through brokerage, the discipline of risk management, the globalization of risk management services and the development of service platforms that identify, quantify, mitigate and transfer risk.

Currently, approximately 45,800 Marsh colleagues provide risk management, insurance broking, insurance program management, risk consulting, analytical modeling and alternative risk financing services to a wide range of businesses, government entities, professional service organizations and individuals in over 130 countries. Marsh generated approximately 51% of the Company's total revenue in 2023.

Insurance Broking and Risk Advisory

In its core insurance broking and risk advisory business, Marsh employs a team approach to identify, quantify and address clients' risk management and insurance needs. Marsh’s product and service offerings include risk analysis, insurance program design and placement, insurance program support and administration, claims support and advocacy, alternative risk strategies and a wide array of risk analysis and risk management consulting services. Clients benefit from Marsh’s advanced analytics, deep technical expertise, specialty and industry knowledge, collaborative global culture and the ability to develop innovative solutions and products. The firm’s resources also include nearly three dozen specialty and industry practices, including cyber, construction, renewable energy, healthcare, and financial and professional service practices, along with ESG products such as

a D&O insurance initiative recognizing U.S. based clients with superior ESG frameworks, and an established employee health & benefits business.

Marsh provides services to clients of all sizes, including large multinational companies ("Risk Management"), high growth middle-market businesses ("Corporate"), small commercial enterprises and high net-worth private clients, and affinity group members ("Commercial & Consumer"). Marsh's segments are designed to build stronger value propositions and operating models to optimize solutions and services for clients depending on their needs.

Risk Management. Marsh has an extensive global footprint and market-leading advisory and placement services that benefit large domestic and international companies and institutions facing complex risk exposures. These clients are also supported by Marsh’s robust analytics and a growing digital experience.

In addition, Marsh’s largest global clients are serviced by Marsh Multinational, a dedicated team of colleagues from around the world focused on delivering service excellence and insurance solutions to clients wherever they are located. Marsh is digitizing the client experience through tools such as LINQ, Marsh’s account and service application; Blue[i], a suite of analytics tools for clients; and Bluestream, a digital brokerage platform that enables clients to provide insurance to their customers or suppliers in a B2B2C distribution model. Marsh provides global expertise and an intimate knowledge of local markets, helping clients navigate local regulatory environments to address the worldwide risk issues that confront them.

• Marsh Specialty** is an integrated and globally coordinated team of experts who provides clients in highly specialized industry and product areas with data driven insights, service, advice and access to global insurance markets. These specialists support clients who require advice and support across aviation & space, credit specialties, construction, energy & power, financial & professional services (FINPRO), marine & cargo, and private equity, mergers & acquisitions (PEMA).

Corporate. Middle market clients are served by Marsh’s brokerage operations globally; this segment is also serviced by Marsh & McLennan Agency (MMA) in the United States (U.S.).

• Marsh McLennan Agency (MMA)** provides business insurance, employee health and benefits, retirement and wealth management, and private client insurance solutions to individuals and mid-market organizations. MMA advises on insurance program structure and market dynamics, along with industry expertise and transactional capability. Since its first acquisition in 2009, MMA has acquired more than 100 agencies.

Commercial & Consumer. Clients in this market segment typically face less complex risks and are served by Marsh’s innovative product and placement offerings and growing capabilities in digitally enabled distribution and administration.

• Victor Insurance Managers (Victor**) is one of the largest underwriting managers of professional liability, catastrophe, and other specialty insurance programs worldwide. In the U.S., Victor Insurance Managers (US) and ICAT Managers underwrites, solicits, sells and services coverages through a national third-party distribution network of licensed brokers and agents. Through its Victor Small Business platform, Victor deploys cloud-based technology to enable independent insurance agents, on behalf of their small business clients, to obtain online quotes from multiple insurance providers and bind property and casualty and workers compensation insurance policies in real time. Victor also manages Torrent Technologies, the nation’s largest service provider to the National Flood Insurance Program (NFIP), serving the NFIP both directly and through the NFIP’s Write Your Own (WYO) program. Victor Insurance Managers (Canada), a leading managing general agent in Canada, delivers professional liability and construction insurance and other P&C programs and administers group and retiree benefits programs and claims handling operations for individuals, organizations and businesses. Victor also has a business in the UK, the Netherlands, Italy, Germany and Australia.

• Marsh Affinity** focuses on insurance programs sold to insureds or vendors through a corporate sponsor using an affinity distribution model.

• High Net Worth (HNW).** Individual high net worth clients and family offices are serviced by MMA in the U.S. and other Marsh personal lines businesses globally. These businesses provide a single-source solution for high net worth clients and are dedicated to sourcing protections across a broad spectrum of risk. Using a consultative approach, Marsh's HNW practices analyze exposures and customize programs to cover individual clients with complex asset portfolios.

Additional Services and Adjacent Businesses

In addition to insurance broking, Marsh provides certain other specialist advisory or placement services:

Marsh Advisory is a global practice comprising specialists who use data and analytics, including through Marsh’s Blue[i] digital analytics platform. Marsh Advisory’s three main service areas (Consulting, Claims, and Analytics) advise clients on existing and emerging risk exposures, protecting critical business activities and developing strategies to optimize total cost of risk.

Marsh Captive Solutions*,* a prominent part of the Marsh Specialty and Global Placement practice, helps organizations of all sizes retain risks through comprehensive and innovative captive solutions. This team is comprised of captive consultants, actuaries and captive management professionals which offer complete, end-to-end captive management services.

Bowring Marsh is an international placement broker. This unit’s core strategy is to modernize risk transfer advice and solutions for clients. This is executed through a combination of data solutions, capacity creation vehicles, segmentation, placement platforms (on-shoring solutions within the network), and improved operational efficiency – all designed to yield a better client outcome and experience. The products Bowring Marsh places include property, casualty, terrorism, product recall, and special risks.

Mercer Marsh Benefits provides health benefits brokerage and consulting services to clients of all sizes in numerous countries across the globe, outside of the U.S. As described below, Mercer and Marsh go to market together to provide strategic advice and services to help clients minimize risk, optimize benefits structure, drive efficiencies and maximize employee engagement.

Services for Insurers

Marsh's Insurer Consulting Group (ICG) provides services to insurance carriers. Through Marsh's patented electronic platform, MarketConnect, and sophisticated data analysis, ICG provides insurers with individualized preference setting and risk identification capabilities, as well as detailed performance data and metrics. Insurer consulting teams review performance metrics and preferences with insurers and provide customized consulting services to insurers designed to improve business planning and strategy implementation. ICG services are designed to improve the product offerings available to clients, assist insurers in identifying new opportunities and enhance insurers’ operational efficiency. The scope and nature of the services vary by insurer and by geography.

GUY CARPENTER

Guy Carpenter, the Company’s reinsurance intermediary and advisor, generated approximately 11% of the Company's total revenue in 2023. Currently, approximately 3,500 Guy Carpenter colleagues provide clients with a combination of specialized reinsurance broking expertise, strategic advisory services and analytics solutions. Guy Carpenter creates and executes reinsurance and risk management solutions for clients worldwide through risk assessment analytics, actuarial services, highly-specialized product knowledge and trading relationships with reinsurance markets. Client services also include contract and claims management, reinsurance accounting and fiduciary services.

Acting as a broker or intermediary on all classes of reinsurance, Guy Carpenter places two main types of property casualty and life / health reinsurance: treaty reinsurance, which involves the transfer of a portfolio of risks; and facultative reinsurance, which involves the transfer of part or all of the coverage provided by a single insurance policy.

Guy Carpenter provides reinsurance services in a broad range of centers of excellence, segments and specialties including: Automobile / Motor, Aviation, Captives, Crop/Agriculture, Cyber, Engineering / Construction, Financial Lines, InsurTech, Life / Accident / Health, Marine and Energy, Medical Professional, Personal Lines, Mortgage, Political Risk & Trade Credit, Primary & Excess Casualty, Managing General Agents and Program Manager Solutions, Property, Public Sector, Regional / Mutual, Retrocessional Reinsurance, Surety, Terror, and Workers Compensation / Employer Liability.

Guy Carpenter also offers clients alternatives to traditional reinsurance, including industry loss warranties and, through its licensed affiliates, capital markets alternatives such as transferring catastrophe risk through the issuance of insurance-linked securities. GC Securities, the Guy Carpenter division of MMC Securities LLC and MMC Securities (Europe) Limited, offer corporate finance solutions, including mergers & acquisitions advice and private debt and equity capital raising, and capital markets-based risk transfer solutions that complement Guy Carpenter's strong industry relationships, analytical capabilities and reinsurance expertise.

Guy Carpenter also provides its clients with reinsurance-related services, including actuarial, enterprise risk management, financial and regulatory consulting, portfolio analysis and advice on the efficient use of capital. Guy Carpenter's Global Strategic Advisory ("GSA") unit helps clients better understand and quantify the uncertainties inherent in their businesses. Working in close partnership with Guy Carpenter account executives, GSA specialists help support clients' critical decisions in numerous areas, including reinsurance utilization, catastrophe exposure portfolio management, new product and market development, rating agency, regulatory and account impacts, loss reserve risk, capital adequacy and return on capital.

Compensation for Services in Risk and Insurance Services

Marsh and Guy Carpenter are compensated for brokerage and consulting services through commissions and fees. Commission rates and fees vary in amount and can depend on a number of factors, including the type of insurance or reinsurance coverage provided, the particular insurer or reinsurer selected, and the capacity in which the broker acts and negotiates with clients. In addition to compensation from its clients, Marsh also receives other compensation, separate from retail fees and commissions, from insurance companies. This other compensation includes, among other things, payments for consulting and analytics services provided to insurers; compensation for administrative and other services (including fees for underwriting services and services provided to or on behalf of insurers relating to the administration and management of quota shares, panels and other facilities in which insurers participate); and contingent commissions, which are paid by insurers based on factors such as volume or profitability of Marsh's placements, primarily driven by MMA and parts of Marsh's international operations.

Marsh and Guy Carpenter receive interest income on certain funds (such as premiums and claims proceeds) held in a fiduciary capacity for others. For a more detailed discussion of revenue sources and factors affecting revenue in our Risk and Insurance Services segment, refer to Part II, Item 7 ("Management's Discussion and Analysis of Financial Condition and Results of Operations") of this report.

CONSULTING

The Company's Consulting segment generated approximately 38% of the Company's total revenue in 2023 and employs approximately 31,300 colleagues worldwide. The Company conducts business in this segment through Mercer and Oliver Wyman Group.

MERCER

Mercer is a leading provider in delivering advice, solutions and products that help organizations meet the health, wealth and career needs of a changing workforce. Mercer has approximately 24,500 colleagues based in 48 countries. Clients include a majority of the companies in the Fortune 1000 and FTSE 100, as well as medium- and small-market organizations, public sector entities and individual customers. Mercer generated approximately 24% of the Company's total revenue in 2023.

Mercer operates in the following areas:

Health. Mercer helps public and private sector employers design and manage employee health and welfare programs; administer health benefits and flexible benefits programs, including benefits outsourcing; engage employees with their health benefits through a digital experience; and comply with local benefits-related regulations. Mercer provides a range of advice and solutions to clients, which, depending on the engagement, may include: total health and wellness management strategies; global health brokerage solutions; vendor performance and audit; life and disability management; and measurement of healthcare provider performance. These services are provided through fee-based consulting as well as commission-based brokerage services in connection with the selection of insurance companies and healthcare providers.

Mercer also provides consulting and actuarial services to U.S. state governments to support the purchase of healthcare through state Medicaid programs. Mercer offers clients tools to enhance employee engagement with their health benefits through its DarwinSM platform.

Outside of the U.S., Mercer and Marsh go to market together for Health benefits brokerage and consulting under the Mercer Marsh BenefitsSM (MMB) brand, as described above.

Wealth. Through its Wealth business, Mercer assists clients worldwide in the design, governance and risk management of defined benefit, defined contribution, hybrid retirement plans and other pools of assets, and with investment of those assets.

Mercer provides actuarial consulting, investment consulting, investment management and related services to the sponsors and trustees of pension plans, master trusts, foundations, endowments, sovereign wealth funds, insurance companies and family offices. Mercer also provides investment consulting and investment management services to U.S. public sector clients, financial intermediaries and individuals. Mercer provides retirement plan outsourcing, including administration and delivery of defined benefit and defined contribution retirement benefits.

Mercer's investment consulting and investment management services (investment management services may also be referred to as "investment solutions," "delegated solutions," "fiduciary management" or "outsourced Chief Investment Officer (OCIO) services") cover a range of stages of the investment process, from investment research (through its Mercer-Insight service), asset allocation and implementation of investment strategies to ongoing portfolio management services. Mercer provides these services primarily to institutional and other sophisticated investors including retirement plans (e.g., defined benefit and defined contribution), master trusts, endowments and foundations, sovereign wealth funds, U.S. public sector clients, insurance companies and family offices, as well as wealth managers and other financial intermediaries, primarily through manager of manager strategies and funds sponsored and managed by Mercer. Mercer’s clients invest in both traditional asset classes (e.g., equities, fixed income and cash equivalents) and alternative or private market strategies (e.g., private equity, private debt, real estate, other real assets and hedge funds). As of December 31, 2023, Mercer and its global affiliates had assets under management of approximately $420 billion worldwide.

Mercer also provides services to individual retail clients, including financial planning, high net worth risk solutions and other discretionary investment services.

Career. Mercer advises organizations on the engagement, skill assessment, management and reward of employees; the design of executive remuneration programs; people and workforce strategies during business transformation; improvement of human resource (HR) effectiveness; and the implementation of digital and cloud-based Human Resource Information Systems. In addition, through proprietary survey data and decision support tools, Mercer provides clients with human capital information and analytical capabilities to improve strategic human capital decision making. Mercer’s Career products include solutions relating to rewards, mobility, engagement, workforce analytics and assessments. Mercer helps clients plan and implement HR programs and other organizational changes designed to maximize employee engagement.

Mercer also provides advice relating to people and benefits-related issues to buyers and sellers in a variety of types of M&A transactions.

OLIVER WYMAN GROUP

With more than 6,800 professionals and offices in over 30 countries, Oliver Wyman Group delivers advisory services to clients through three operating units, each of which is a leader in its field: Oliver Wyman, Lippincott and NERA Economic Consulting. Oliver Wyman Group generated approximately 14% of the Company's total revenue in 2023.

Oliver Wyman is a global leader in management consulting and combines deep industry knowledge with specialized expertise in strategy, operations, risk management and organization transformation. The firm works with clients around the world to help optimize their business, improve their operations and risk profile, and accelerate their organizational performance to seize attractive opportunities. Industry groups include:

• Automotive and Manufacturing Industries

• Communications, Media & Technology

• Energy and Natural Resources

• Financial Services (including corporate and institutional banking, public policy, and retail and business banking)

• Insurance and Asset Management

• Health and Life Sciences

• Public Sector

• Private Capital

• Retail & Consumer Goods

• Transportation Services (including aviation; aerospace and defense; rail; express, postal and third party logistics; services, including travel and leisure, environmental and facility management, and business and tech services; and CAVOK, which provides technical consulting and market forecasting services)

Oliver Wyman overlays its industry knowledge with expertise in the following functional specializations:

• Actuarial. Oliver Wyman’s Actuarial Practice uses mathematical and statistical modeling skills and qualitative assessment methodologies to assist clients in evaluating and addressing risk.

• Climate and Sustainability. Oliver Wyman assists clients in cutting through complex climate systems and solving for operational efficiencies. Oliver Wyman helps clients discover new business opportunities, create new pathways, and respond to climate risk, to make needed changes commercially compelling.

• Finance and Risk. Oliver Wyman provides leading financial institutions with custom solutions and insights covering all aspects of risk and finance functions, including credit risk, market risks, asset and liability management and liquidity risks, and non-financial risks, together with integrated risk management topics, such as aggregated risk analyses, business applications and culture and organization.

• Restructuring. Oliver Wyman offers a complete management solution and "one-stop-shop" approach to turning around companies, providing strategic, operational, and financial restructuring advice.

• Digital. Oliver Wyman partners with clients to address their digital challenges, blending the power of digital with deep industry expertise. By building strong capabilities and culture, Oliver Wyman accelerates and embeds digital transformation, working collaboratively with clients’ leaders, employees, stakeholders, and customers to jointly define, design, and achieve lasting results.

• Operations. Oliver Wyman helps organizations leverage their operations for a competitive advantage using a comprehensive set of capabilities, including performance improvement, digital operations strategy, and risk management.

• People and Organizational Performance. Oliver Wyman's People and Organizational Performance capability brings together deep functional expertise and industry knowledge to enable the whole organization to work in service of its strategic vision and to address the most pressing organizational, people, and change issues.

• Payments. Oliver Wyman draws on years of industry-shaping work in the Financial Services and Retail industries, deep digital expertise, and renowned research partners in its Celent® business, to help clients - from banks/issuers, to payments providers, to retailers - to build growth strategies, form effective partnerships, optimize costs, and manage risk.

• Pricing, Sales, and Marketing. Oliver Wyman helps organizations drive top-line and margin growth through outstanding strategy and decision making on pricing, marketing optimization, and best practices on sales effectiveness.

• Customer First. Oliver Wyman helps bring together capabilities required to identify customer and business growth, conduct detailed business design, build and launch a business, and maintain a focus on realizing growth while de-risking delivery.

• Performance Transformation. Oliver Wyman helps clients to design, realize and sustain value growth via large-scale transformations.

Lippincott is a creative consultancy specializing in brand and innovation that shapes recognized brands and experiences for clients globally. Lippincott's designers have helped create some of the world's most recognized brands.

NERA Economic Consulting provides economic analysis and advice to public and private entities to achieve practical solutions to highly complex business and legal issues arising from competition, regulation, public policy, strategy, finance and litigation. NERA professionals operate worldwide assisting clients including corporations, governments, law firms, regulatory agencies, trade associations, and international agencies. NERA's specialized practice areas include: antitrust; securities; complex commercial litigation; energy; environmental economics; network industries; intellectual property; product liability and mass torts; and transfer pricing.

Compensation for Services in Consulting

Oliver Wyman Group is compensated for advice and services primarily through fees paid by clients. Mercer is compensated for advice and services through fees paid by clients, commissions and fees based on assets or members. In the majority of cases, Mercer's Health business is compensated through commissions for the placement of insurance contracts and supplemental compensation from insurers based on such factors as volume, growth of accounts, and total retention of accounts placed by Mercer. Mercer may receive commissions in other parts of its business, such as its Private Client Services business and certain financial advice businesses. Mercer's investments business and certain of Mercer's administration services are compensated typically through fees based on assets under administration or management or fee per member. For a majority of the Mercer-managed investment funds, revenue received from Mercer's investment management clients as sub-advisor fees is reported in accordance with U.S. GAAP, on a gross basis rather than a net basis. For a more detailed discussion of revenue sources and factors affecting revenue in the Consulting segment, refer to Part II, Item 7 ("Management's Discussion and Analysis of Financial Condition and Results of Operations") of this report.

REGULATION

The Company's activities are subject to licensing requirements and extensive regulation under U.S. federal and state laws, as well as laws of other countries in which the Company operates. Across most jurisdictions, we are also subject to various data privacy and data protection laws and regulations that apply to personal information, as well as, in certain jurisdictions, cybersecurity laws and regulations and emerging laws and regulations related to artificial intelligence ("AI"). In addition, we are subject to various financial crime laws and regulations through our activities, activities of associated persons, the products and services we provide and our business and client relationships. Such laws and regulations relate to, among other areas, sanctions and export control, anti-bribery, anti-corruption, anti-money-laundering and counter-terrorist financing. In certain circumstances, we are also required to maintain operating funds primarily related to regulatory requirements outside the U.S. See Part I, Item 1A ("Risk Factors") below for a discussion of how actions by regulatory authorities or changes in legislation and regulation in the jurisdictions in which we operate may have an adverse effect on our businesses and for more information about the laws and regulations related to data privacy, data protection and cybersecurity and the associated risks to our businesses.

Risk and Insurance Services**.** While laws and regulations vary from location to location, every state of the U.S. and most foreign jurisdictions require insurance market intermediaries and related service providers (such as insurance brokers, agents and consultants, reinsurance brokers and managing general agents) to hold an individual or company license from a government agency or self-regulatory organization. Some jurisdictions issue licenses only to individual residents or locally-owned business entities; in those instances, if the Company has no licensed subsidiary, it may maintain arrangements with residents or business entities licensed to act in such jurisdiction. Such arrangements are subject to an internal review and approval process. Licensing of reinsurance intermediaries is generally less rigorous compared to that of insurance brokers, and most jurisdictions require only corporate reinsurance intermediary licenses.

In the United Kingdom, our business is regulated by the Financial Conduct Authority ("FCA"). The FCA’s responsibilities and powers include licensing of insurance and reinsurance intermediaries and related criteria such as professional competence, financial capacity and the requirement to hold professional indemnity insurance, the broking of premium finance to consumers, and competition powers that enable it to enforce prohibitions on anti-competitive behavior in relation to financial services.

Insurance authorities in the U.S. and certain other jurisdictions in which the Company's subsidiaries do business, including the FCA in the United Kingdom, also have enacted laws and regulations governing the investment of funds, such as premiums and claims proceeds, held in a fiduciary capacity for others. These laws and regulations typically provide for segregation of these fiduciary funds and limit the types of investments that may be made with them, and generally apply to both the insurance and reinsurance business.

Certain of the Company's Risk and Insurance Services activities are governed by other regulatory bodies, such as investment, securities and futures licensing authorities. In the U.S., Marsh and Guy Carpenter use the services of MMC Securities LLC, a SEC registered broker-dealer and introducing broker in the U.S. MMC Securities LLC is a member of the Financial Industry Regulatory Authority ("FINRA"), the National Futures Association and the Securities Investor Protection Corporation ("SIPC"), primarily in connection with capital markets and other investment banking-related services relating to insurance-linked and alternative risk financing transactions. Also in the U.S., Marsh uses the services of MMA Securities LLC, a SEC registered broker-dealer, investment adviser

and member of FINRA, SIPC and the Municipal Securities Rulemaking Board ("MSRB"), and MMA Asset Management LLC, a SEC registered investment adviser, primarily in connection with retirement, executive compensation and benefits consulting and advisory services to qualified and non-qualified benefits plans, companies and executives and personal wealth management. In the United Kingdom, Marsh and Guy Carpenter use the expertise of MMC Securities Limited, which is authorized and regulated by the FCA to provide advice on securities and investments, including mergers & acquisitions in the United Kingdom. In the European Union, Guy Carpenter uses MMC Securities (Ireland) Limited, which is authorized and regulated by the Central Bank of Ireland to place certain securities and investments in the European Union. MMC Securities LLC, MMC Securities Limited, MMC Securities (Ireland) Limited, MMA Securities LLC, and MMA Asset Management LLC are indirect, wholly-owned subsidiaries of Marsh & McLennan Companies, Inc.

Consulting*.* Mercer's retirement-related consulting and investment services are subject to pension law and financial regulation in many countries. Depending on the country, Mercer may rely on licensed colleagues or registered legal entities to engage in these services, or may utilize other Marsh McLennan entities or third parties. In addition, trustee services, investment services (including advice to persons, institutions and other entities on the investment of pension assets and assumption of discretionary investment management responsibilities) and retirement and employee benefit program administrative services provided by Mercer and its subsidiaries and affiliates may also be subject to investment and securities regulations in various jurisdictions, including (but not limited to) regulations imposed or enforced by the Securities and Exchange Commission (SEC) and the Department of Labor in the U.S., the FCA in the United Kingdom, the Central Bank of Ireland and the Australian Prudential Regulation Authority and the Australian Securities and Investments Commission. In the U.S., Mercer provides investment services through Mercer Investments LLC, (formerly Mercer Investment Management, Inc.), an SEC-registered investment adviser, which consolidated the activities of each of Mercer’s affiliated investment adviser entities in the U.S. (including Mercer Investment Consulting LLC and Pavilion Advisory Group) in 2019. Mercer Trust Company, a limited purpose New Hampshire chartered trust bank, may also provide services for certain clients of Mercer’s investment management business in the U.S. The benefits insurance consulting and brokerage services provided by Mercer and its subsidiaries and affiliates are subject to the same licensing requirements and regulatory oversight as the insurance market intermediaries described above regarding our Risk and Insurance Services businesses. Depending on the nature of the client and services performed, Mercer may also be subject to direct oversight by the Departments of Health and Human Services and other federal agencies in the U.S. Mercer provides annuity buy-out advice that is subject to regulations (for example, in the U.S., state insurance licensing regulations and ERISA). Mercer uses the services of MMC Securities LLC to provide certain services, including executive benefit and compensation services and securities dealing services.

FATCA**.** Regulations promulgated by the U.S. Treasury Department pursuant to the Foreign Account Tax Compliance Act and related legislation (FATCA) require the Company to take various measures relating to non-U.S. funds, transactions and accounts. The regulations impose on Mercer and MMA certain client financial account obligations relating to non-U.S. financial institution and insurance clients.

COMPETITIVE CONDITIONS

The Company faces significant competition in all of its businesses from providers of similar products and services, including competition with regard to identifying and pursuing acquisition candidates. The Company also encounters strong competition throughout its businesses from both public corporations and private firms in attracting and retaining qualified employees. As the Company has clients across various geographies, industries and sizes, the competitive landscape is complex and varies across numerous markets. In addition to the discussion below, refer to "Risks Relating to the Company Generally — Competitive Risks," in Part I, Item 1A of this report.

Risk and Insurance Services**.** The Company's combined insurance and reinsurance services businesses are global in scope. Our insurance and reinsurance businesses compete principally on the sophistication, range, quality and cost of the services and products they offer to clients. The Company encounters strong competition from other insurance and reinsurance brokerage firms that operate on a global, regional, national or local scale in every geography in which it operates, from insurance and reinsurance companies that market, distribute and service their insurance and reinsurance products without the assistance of brokers and from other businesses, including commercial and investment banks, accounting firms, consultants and online platforms, that provide risk-related services and products or alternatives to traditional insurance brokerage services. In addition, third party capital providers have entered the insurance and reinsurance risk transfer market offering products and capital

directly to the Company’s clients. Their presence in the market increases the competitive pressures that the Company faces.

Certain insureds and groups of insureds have established programs of self-insurance as a supplement or alternative to purchasing traditional third-party insurance, thereby reducing in some cases their need for third-party insurance placements. Certain insureds also obtain coverage directly from insurance providers. There are also many other providers of managing general agents, affinity programs and private client services that compete with the Company's offerings.

Consulting**.** The Company's consulting businesses face strong competition from other privately and publicly held worldwide and national companies, as well as regional and local firms. These businesses generally compete on the basis of the range, quality and cost of the services and products they provide to clients. Competitors include independent consulting, broking and outsourcing firms, as well as consulting, broking and outsourcing operations affiliated with larger accounting, information systems, technology and financial services firms. Mercer’s Health business faces additional competition from insurers and from non-traditional competitors seeking to enter or expand in the health benefits space (for example, payroll firms, large consumer businesses, and digitally oriented consultancies). Mercer's investments business faces competition from many sources, including investment consulting firms (many of which offer delegated services), investment management firms and other financial institutions. In some cases, clients have the option of handling the services provided by Mercer and Oliver Wyman Group internally, without assistance from outside advisors.

Segmentation of Activity by Type of Service and Geographic Area of Operation.

Financial information relating to the types of services provided by the Company and the geographic areas of its operations is incorporated herein by reference to Note 17, Segment Information, in the notes to the consolidated financial statements included under Part II, Item 8 of this report.

ENVIRONMENTAL, SOCIAL AND GOVERNANCE (ESG)****)

Since 2008, Marsh McLennan has had a framework for overseeing and managing the company’s approach to environmental sustainability, human capital management and corporate governance. Our ESG Report provides more information about our ESG governance, goals and achievements. It also discloses against aspects of the Task Force on Climate-related Financial Disclosures, Sustainability Accounting Standards Board and Global Reporting Initiative standards and describes the six UN Sustainable Development Goals we have prioritized that most relate to our business. Our ESG Report, Pay Equity Statement, statement on Human Rights and related information is available on our website at marshmclennan.com/about/esg.html. These reports and our website are not deemed part of this report and are not incorporated by reference.

HUMAN CAPITAL

As a professional services firm, we believe the health of our business relies on the strength of our workforce.

For detailed information regarding our human capital management, we encourage investors to visit https://www.marshmclennan.com/about/esg.html for our consolidated ESG Report. The information on this website, and in the ESG report, does not constitute, and should not be viewed as, incorporation by reference of the information contained on, or available through, the website or the report and does not form part of this Form 10-K.

Our People. As of December 31, 2023, the Company and its consolidated subsidiaries employed more than 85,000 colleagues worldwide, including approximately 49,300 in Risk and Insurance Services and 31,300 in Consulting. One-third of our global workforce is located in the U.S. & Canada, with approximately 15% in each of the United Kingdom, Europe and IMEA (India, Middle East, & Africa), with the remainder in Latin America & Caribbean, Asia, and Pacific. Women comprise more than half of our global enterprise workforce, and approximately 33% of our senior leaders are women. In the U.S., where we have the most complete data through workforce self-identification of race and ethnicity, approximately 1 in 4 U.S. colleagues and 18% of U.S. senior leaders identify as non-White.

Our Governance. The Chief People Officer is responsible for developing and executing our enterprise people strategy. This includes the attraction, recruitment, hiring, development and engagement of talent to deliver on our strategy and the design of colleague total rewards programs. The Chief People Officer is also responsible for developing and integrating our inclusion and diversity approach into our strategy, supported by the Chief Diversity & Social Impact Officer.

Talent & Inclusion. Our Company’s greatest strength is the collective talent of our people. We offer programs globally, regionally and business-specific that are aimed at helping us attract, develop and retain a diverse workforce. We provide resources to support colleagues in learning about diverse experiences, connecting with each other and positively impacting communities. We are committed to helping colleagues perform at their best by encouraging regular discussions about their goals, performance, career aspirations and development opportunities. We offer programming to support their growth and activate a leadership mindset for all colleagues.

We also aim to build a learning culture and deliver a digital-first learning strategy, supplemented by formal programs for key groups. For example, our 2023 Learning Festival offered 31 live sessions in 8 languages with over 18,000 attendees. Top sessions included business briefings with our CEOs, the future of insurance, cyber resilience and AI.

We also recognize the importance of our nearly 18,000 people managers to our talent pipeline and have given them increased support and opportunities for promoting the growth of their teams. In 2023 we offered 450 development workshops with courses covering professional skills, people management and leadership development. Our People Manager Hub is a one-stop digital source for people managers globally. Through the Hub, people managers have access to suggested learning, webinars and resources to support development and provide guidance.

Colleague Engagement. Each year we ask our colleagues to share their views on working at Marsh McLennan through a company-wide engagement survey. Developed internally by our Global Talent Development team, the survey methodology has been consistent since 2011, with updates to specific questions as necessary. In 2023, we expanded the survey with questions on technology and the company's strategy. A third-party administers our survey in order to maintain confidentiality of responses. Collective survey outcomes allow us to monitor the evolution of our culture over time and identify opportunities to build on strengths and address challenges, all with the intention of furthering our productivity through an engaged workforce.

Health and Well-being. As a company, our success depends on the health and well-being of our colleagues. We offer comprehensive health insurance, including medical coverage and other core health benefits based on the market. We also prioritize our colleagues’ mental wellness, including 24/7 access to an Employee Assistance Program for confidential counselling on personal issues for 99% of our colleagues and their eligible family members, and critical incident support in countries where a disaster has occurred. In addition, we offer competitive time-off benefits, including a paid day off each year to volunteer. We support our colleagues as they navigate changing circumstances—milestone life events, health and economic challenges, and new technologies.

Total Rewards. We offer competitive rewards to help build colleagues’ personal wealth and improve their financial well-being. Base pay is one component. Through our annual bonus program, we encourage performance that aligns with the Company’s interests by providing eligible colleagues with discretionary awards. We also offer various incentives in certain circumstances, such as sales incentives and long-term incentives to people in roles that have a significant impact on our long-term performance and success. Our offerings also include retirement benefits, savings and stock investment plans in certain jurisdictions.

EXECUTIVE OFFICERS OF THE COMPANY

The executive officers and executive officer appointees of the Company are appointed annually by the Company’s Board of Directors. The following individuals are the executive officers of the Company as of February 12, 2024:

Paul Beswick, age 49, is Senior Vice President and Global Chief Information Officer (CIO) of Marsh McLennan. In this role, he manages over 5,000 technologists supporting Marsh McLennan’s global businesses. Prior to his appointment as Marsh McLennan CIO in January 2021, Mr. Beswick was a Partner and Global Head of Oliver Wyman Labs and the Digital Practice at Oliver Wyman. During more than two decades with Oliver Wyman, he worked in various sectors, including retail, transportation, telecom, and consumer goods. Before this, Mr. Beswick headed Oliver Wyman's North American Retail Practice. Mr. Beswick holds an MA (first class) in chemical engineering from Cambridge University.

Katherine J. Brennan, age 45, is Senior Vice President and General Counsel of Marsh McLennan. In this role, she leads Marsh McLennan’s global legal, compliance and public affairs function, which supports the Company’s four businesses, Marsh, Guy Carpenter, Mercer and Oliver Wyman. She also leads the Company’s ESG efforts. Ms. Brennan has held several legal and compliance leadership roles at Marsh McLennan, serving most recently as General Counsel, Marsh LLC. She also served as Deputy General Counsel, Corporate Secretary and Chief Compliance Officer for Marsh McLennan from 2017 to 2021, and prior to that, as General Counsel of Guy Carpenter. Ms. Brennan currently serves on the Board of the Red Cross of Greater New York.

John Q. Doyle, age 60, is President and Chief Executive Officer of Marsh McLennan. Previously, from 2021 to 2022 he served as Group President and Chief Operating Officer, responsible for the strategy and operational objectives of Marsh McLennan’s four global businesses. He joined the firm in 2016 as President of Marsh, then led Marsh as President and CEO from 2017 to 2021. An industry veteran with more than 35 years of management experience, Mr. Doyle began his career at AIG, where he held several executive positions. He is a member of the Board of the New York Police and Fire Widows’ and Children’s Benefit Fund, a Trustee of the Inner-City Scholarship Fund, a member of the Board of Overseers of the Maurice R. Greenberg School of Risk Management, Insurance and Actuarial Science at St. John’s University and a former Director of the American Insurance Association. Mr. Doyle serves as the Chairman of the U.S. Federal Advisory Committee on Insurance.

Martine Ferland, age 62, is Chief Executive Officer of Mercer. She also serves as Vice Chair of Marsh McLennan. Prior to assuming her current role in March 2019, she was Mercer’s Group President, responsible for leading the firm’s regions and Global Business Solutions. She joined Mercer in 2011 as Retirement Business Leader for EMEA, and has served as Europe and Pacific Region President and Co-President, Global Health. Ms. Ferland began her career as a pension actuary and consultant at Willis Towers Watson, where she spent 25 years and held various leadership positions in Montreal and New York. Ms. Ferland is a Fellow of the Society of Actuaries and of the Canadian Institute of Actuaries and a member of the Board of Trustees of the New York Academy of Medicine.

Carmen Fernandez, age 50, is Senior Vice President and Chief People Officer for Marsh McLennan. Prior to her appointment as Chief People Officer in January 2021, Ms. Fernandez held positions within Marsh McLennan for 15 years, most recently Deputy CHRO, CHRO of Guy Carpenter, and HR leadership roles at Mercer, including North America HR Leader, Global HR Leader for the Career business and Chief of Staff in the Office of the CEO. Before joining Marsh McLennan, Ms. Fernandez worked in investment banking at Bank of America and Goldman Sachs. She began her career as a consultant with PricewaterhouseCoopers.

John Jones, age 52, is Chief Marketing and Communications officer of Marsh McLennan. Previously, he served as Chief Marketing and Communications Officer of Marsh from 2018 to 2022. Mr. Jones joined Marsh in 2016 as senior vice president of Marsh’s business planning, leading strategic planning and global growth initiatives. Prior to that, Mr. Jones was senior vice president of commercial marketing and strategy for AIG and has more than 25 years of marketing, communications and strategy experience.

Dean Klisura, age 60, is President and Chief Executive Officer of Guy Carpenter and serves as Vice Chair of Marsh McLennan. Prior to assuming this role in January 2022, he was President of Guy Carpenter, overseeing the North America, International, Specialty and Global Strategic Advisory business units. Prior to joining Guy Carpenter, Mr. Klisura was President of Marsh Global Placement and Advisory Services, leading property and casualty placement activities globally, as well as leading Bowring Marsh, the Insurer Consulting Group, and Marsh Advisory. He joined Marsh in 1993 and held several key global leadership roles including President of Global Specialties.

Mark McGivney, age 56, is Chief Financial Officer of Marsh McLennan. Prior to assuming this role in January 2016, Mr. McGivney held a number of senior financial management positions since joining the Company in 2007. Most recently he was Senior Vice President, Corporate Finance of Marsh McLennan, and was responsible for leading and directing the Company’s Corporate Development, Treasury and Investor Relations functions from 2014 until 2016. Prior to that, he served as Chief Financial Officer of Marsh, and Chief Financial Officer and Chief Operating Officer of Mercer. His prior experience includes senior positions at The Hanover Insurance Group, including serving as Senior Vice President of Finance, Treasurer, and Chief Financial Officer of the Property & Casualty business, as well as positions with Merrill Lynch and PricewaterhouseCoopers.

Martin South, age 59, is President and Chief Executive Officer of Marsh, a position he assumed in January 2022, and oversees all of Marsh’s businesses and operations globally. He also serves as Vice Chair of Marsh McLennan. With more than 30 years in the insurance industry, Mr. South joined Marsh for the first time in 1985 with Bowring Marsh, a Marsh McLennan broking unit. His industry experience includes senior leadership roles at Zurich Financial Services, where he was a member of the Group Management Board, responsible for all of Zurich’s operations outside of North America and Europe, and CEO of Zurich’s London operations. Since rejoining Marsh in 2007, Mr. South has served as CEO of Marsh’s Asia-Pacific region, CEO of Marsh UK and Ireland, CEO of Marsh Europe and CEO of Marsh U.S. and Canada.

Nicholas Studer, age 50, is Chief Executive Officer of Oliver Wyman Group, a role he assumed in July of 2021. He also serves as Vice Chair of Marsh McLennan. From 2017 to 2021, Mr. Studer was the Managing Partner of the Consumer, Industrial and Services Practice Group, before becoming Managing Partner of Oliver Wyman in 2021. He has held many senior positions at Oliver Wyman including Managing Partner of the Financial Services Practice Group, Head of the European Finance and Risk Practice and Global head of the Corporate and Institutional Banking practice. He has over 25 years of experience consulting in the UK, Continental Europe, and North America.

The Company is subject to the information reporting requirements of the Securities Exchange Act of 1934. In accordance with the Exchange Act, the Company files with, or furnishes to, the SEC its annual reports on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K and proxy statement for its annual shareholders' meeting. The Company makes these reports and any amendments to these reports available free of charge through its website, www.marshmclennan.com, as soon as reasonably practicable after they are filed with or furnished to the SEC. The SEC also maintains a website at www.sec.gov that contains reports, proxy and information statements and other information regarding issuers, like the Company, that file electronically with the SEC.

The Company also posts on its website certain governance and other information for investors.

The Company encourages investors to visit these websites from time to time, as information is updated and new information is posted. Website references in this report are provided as a convenience and do not constitute, and should not be viewed as, incorporation by reference of the information contained on, or available through, the websites. Therefore, such information should not be considered part of this report.

You should consider the risks described below in conjunction with the other information presented in this report. These risks have the potential to materially adversely affect the Company's business, results of operations or financial condition.

SUMMARY RISK FACTORS

Some of the factors that could materially and adversely affect our business, financial condition, results of operations or prospects, include the following:

• Our results of operations and investments could be adversely affected by geopolitical or macroeconomic conditions;

• We are subject to significant uninsured exposures arising from errors and omissions, breach of fiduciary duty and other claims;

• We cannot guarantee that we are or will be in compliance with all current and potentially applicable U.S. federal and state or foreign laws and regulations, and actions by regulatory authorities or changes in legislation and regulation in the jurisdictions in which we operate could have a material adverse effect on our business;

• Our business or reputation could be harmed by our reliance on third-party providers or introducers;

• We may not be able to effectively identify and manage actual and apparent conflicts of interest;

• We could incur significant liability or our reputation could be damaged if our information systems are breached or we otherwise fail to protect client or Company data or information systems;

• The costs to comply with, or our failure to comply with, U.S. and foreign laws related to privacy, data security and data protection, such as the EU's General Data Protection Regulation (GDPR) and the California Consumer Privacy Act, as amended by the California Privacy Rights Act, (CCPA), could adversely affect our financial condition, operating results and our reputation;

• Our business performance and growth plans could be negatively affected if we are not able to develop and implement improvements in technology or respond effectively to the threat of digital disruption and other technological change such as AI;

• The loss of members of our senior management team or other key colleagues, or if we are unsuccessful in our efforts to attract, retain and develop talent, could have a material adverse effect on our business;

• Failure to maintain our corporate culture, particularly in a hybrid work environment, could damage our reputation;

• Increasing scrutiny and changing laws and expectations from regulators, investors, clients and our colleagues with respect to our environmental, social and governance (ESG) practices and disclosure may impose additional costs on us or expose us to new or additional risks;

• We face significant competitive pressures in each of our businesses, including from disintermediation, as our competitive landscape continues to evolve;

• We rely on a large number of vendors and other third parties to perform key functions of our business operations and to provide services to our clients. These vendors and third parties may act or fail to act in ways that could harm our business;

• Our inability to successfully recover should we experience a disaster or other business continuity or data recovery problem could cause material financial loss, loss of human capital, regulatory actions, reputational harm or legal liability;

• We face risks when we acquire or dispose of businesses;

• If we are unable to collect our receivables, our results of operations and cash flows could be adversely affected;

• We may not be able to obtain sufficient financing on favorable terms;

• Our defined benefit pension plan obligations could cause the Company's financial position, earnings and cash flows to fluctuate;

• Our significant non-U.S. operations expose us to exchange rate fluctuations and various risks that could impact our business;

• Our quarterly revenues and profitability may fluctuate significantly;

• Credit rating downgrades would increase our financing costs and could subject us to operational risk;

• Our current debt level could adversely affect our financial flexibility;

• The current U.S. tax regime has provisions which have unintended consequences and may also impact our tax rate in varying degrees based on where our global income is earned;

• We are exposed to multiple risks associated with the global nature of our operations;

• Results in our Risk and Insurance Services segment may be adversely affected by a general decline in economic activity;

• Volatility or declines in premiums and other market trends may significantly impede our ability to grow revenues and profitability;

• Adverse legal developments and future regulations concerning how intermediaries are compensated by insurers or clients, as well as allegations of anti-competitive behavior or conflicts of interest, could have a material adverse effect on Marsh’s business, results of operations and financial condition;

• Mercer’s Wealth business is subject to a number of risks, including risks related to public and private capital market fluctuations, third-party asset managers and custodians, operations and technology risks, conflicts of interest, ESG and greenwashing, asset performance and regulatory compliance, that, if realized, could result in significant damage to our business;

• Revenues for the services provided by our Consulting segment may decline for various reasons, including as a result of changes in economic conditions, the value of equity, debt and other asset classes, our clients’ or an industry's financial condition or government regulation or an accelerated trend away from actively managed investments to passively managed investments;

• Factors affecting defined benefit pension plans and the services we provide relating to those plans could adversely affect Mercer; and

• The profitability of our Consulting segment may decline if we are unable to achieve or maintain adequate utilization and pricing rates for our consultants.

RISKS RELATING TO THE COMPANY GENERALLY

Macroeconomic Risks

Our results of operations and investments could be adversely affected by geopolitical or macroeconomic conditions.

Geopolitical and macroeconomic conditions, including from multiple major wars, escalating conflict throughout the Middle East and rising tension in the South China Sea, slower GDP growth or recession, lower interest rates, capital markets volatility and inflation affect our clients' businesses and the markets they serve. These conditions, including inflationary expense pressure with our clients, may reduce demand for our services or depress pricing for those services, which could have a material adverse effect on our results of operations.

For example, the war in Ukraine and the escalating conflict throughout the Middle East have resulted in worldwide geopolitical and macroeconomic uncertainty and may negatively impact other regional and global economic markets (including Europe, the Middle East and the U.S.), companies in other countries (particularly those that have done business with Russia or have substantial exposure to, or operations in, impacted countries) and various sectors, industries and markets for securities and commodities globally, such as oil and natural gas, and may increase financial market volatility and adversely impact regional and global economic markets, industries and companies. Moreover, the COVID-19 pandemic impacted businesses, including our clients, third-party vendors and business partners, globally in every geography in which we operate. In addition, the potentially divergent laws and regulations as a result of Brexit may continue to lead to economic and legal uncertainty, causing increased economic volatility or disrupting the markets and clients we serve.

Changes in macroeconomic and geopolitical conditions could also shift demand to services for which we do not have a competitive advantage, and this could negatively affect the amount of business that we are able to obtain.

More generally, our investments, inclu

Showing the first 8K of 99K characters. Open the full section

There are no unresolved comments to be reported pursuant to Item 1B.

As a professional services firm that processes confidential and sensitive information, such as personal information, cybersecurity risk management is an integral part of our enterprise risk management strategy. Our cybersecurity risk management program has been designed based on industry standards, such as the National Institute of Standards and Technology Cybersecurity Framework and ISO/IEC:27001, and provides a framework for assessing cybersecurity risk and identifying and managing cybersecurity threats and incidents, including threats and incidents associated with our use of services, applications and products provided by third-party vendors and service providers.

Our cybersecurity risk management program is coordinated by cross-functional teams, including risk management, legal and compliance, business resiliency management and information security. These teams develop, implement and maintain our compliance policies, programs and training, business resiliency, disaster recovery and information security frameworks, solutions and procedures. They also work closely with our business, internal audit, finance and IT staff to identify, assess and mitigate risks, including those associated with our use of third-party vendors and service providers, and to monitor and take steps designed to prevent security incidents in our technology environment.

Our cybersecurity risk management framework includes (1) procedures designed to assess the data privacy and cybersecurity practices of third-party vendors and service providers (including risk assessments and contractual protections), (2) technical IT controls designed to manage risks associated with cybersecurity incidents (such as

multifactor authentication and requirements for VPN or private channel access to our systems), and (3) formal policies and procedures designed to address cybersecurity incidents. Our formal policies and procedures designed to address cybersecurity incidents include steps for verifying and assessing the severity of a cybersecurity incident, identifying the source of a cybersecurity incident (including whether it is associated with a third-party service provider) and implementing cybersecurity countermeasures and mitigation strategies. Additionally, we have procedures for informing senior management and our Board of Directors of potentially material cybersecurity incidents. We also periodically engage third-party security consultants to assess our cybersecurity program and to perform penetration testing on our security environment and controls. In addition, cybersecurity training is provided to all newly hired colleagues and then at least annually for all colleagues. We also conduct regular ongoing cybersecurity awareness campaigns and phishing tests and provide training in response to such tests as appropriate.

Our Board of Directors has overall oversight responsibility for the Company’s risk management and receives updates from management throughout the year on cybersecurity matters and other material risks facing the Company. Additionally, the Audit Committee regularly reviews the Company’s policies and practices with respect to risk assessment and risk management, including cybersecurity risks, and reports to the full Board of Directors on a regular basis. The Audit Committee is responsible for overseeing the Company’s enterprise risk management policies and processes, including discussing with management the Company’s major risk exposures and the steps that have been taken to monitor and control such exposures, including those arising from cybersecurity risks.

Management is responsible for identifying, assessing and managing material cybersecurity risks on an ongoing basis. Management’s efforts include establishing processes designed to ensure that potential cybersecurity risks are monitored, putting in place mitigation and remedial measures and implementing and maintaining cybersecurity programs. Our cybersecurity programs are under the direction of our Chief Information Security Officer (CISO), who reports to our Chief Information Officer (CIO). Our CIO has significant expertise and over a decade of experience working in technology. Our CISO has over twenty years of experience working in cybersecurity and maintains a Certified Information Systems Security Professional certification. Our CISO and CIO receive reports from our cybersecurity team and monitor the prevention, detection, mitigation, and remediation of cybersecurity incidents. Our cybersecurity team is comprised of experienced information systems security professionals and information security managers with many years of experience and various security certifications.

Management, including the CIO and CISO, regularly reviews with the Board of Directors and the Audit Committee the Company’s cybersecurity programs, material cybersecurity risks and mitigation strategies and provides updates on notable developments in the cybersecurity threat landscape. Additionally, management follows a risk-based escalation process to notify the Audit Committee outside of the cycle of regular updates when an emerging risk or material issue is identified, such as a potentially significant cybersecurity threat or incident.

In 2023, we did not identify any cybersecurity threats or incidents that have materially affected or are reasonably likely to materially affect the Company, including with respect to our business strategy, results of operations, or financial condition. However, despite our efforts, we cannot eliminate all risks from cybersecurity threats or incidents, or provide assurances that we have not experienced an undetected cybersecurity threat or incident. For more information about these risks, please see “Risk Factors – Cybersecurity, Data Protection and Technology Risks” in this annual report on Form 10-K.

The Company maintains its corporate headquarters in New York City. We also maintain other offices around the world, primarily in leased space. In certain circumstances we may have space that we sublet to third parties, depending upon our needs in particular locations.

The Company and certain of its subsidiaries own, directly and indirectly through special purpose subsidiaries, a 58% condominium interest covering approximately 900,000 square feet of office space in a 44 story condominium in New York City. This real estate serves as the Company's headquarters and is occupied primarily by the Company and its subsidiaries for general corporate use. The condominium interests are financed by a 30-year mortgage loan that is non-recourse to the Company unless the Company (i) is downgraded below B (stable outlook) by S&P or Fitch or B2 (stable outlook) by Moody's and such downgrade is continuing or (ii) an event of default under the mortgage loan has occurred. The mortgage is secured by a first priority assignment of leases and rents, including the leases which the Company and certain of its subsidiaries entered into with their affiliated special purpose subsidiaries which own the mortgaged condominium interests. The net rent due under those leases in effect services the mortgage debt.

We and our subsidiaries are party to a variety of other legal, administrative, regulatory and government proceedings, claims and inquiries arising in the normal course of business.

Additional information regarding certain legal proceedings and related matters is set forth in Note 16, Claims, Lawsuits and Other Contingencies, in the notes to the consolidated financial statements appearing under Part II, Item 8 ("Financial Statements and Supplementary Data") of this report.

Not applicable.

PART II

The Company’s common stock is listed on the New York and Chicago Stock Exchanges. Effective as of November 27, 2023, the Company’s common stock was delisted from the London Stock Exchange. The following table indicates the high and low prices (NYSE composite quotations) of the Company’s common stock in 2023 and 2022, and each quarterly period thereof:

The Company has a share repurchases program authorized by the Board of Directors.

The Company repurchased approximately 6.4 million shares of its common stock for $1.15 billion in 2023. At December 31, 2023, the Company remained authorized to repurchase up to approximately $3.2 billion in shares of its common stock. There is no time limit on the authorization. The Company repurchased approximately 12.2 million shares of its common stock for $1.9 billion in 2022.

In March 2022, the Board of Directors of the Company authorized an additional $5 billion in share repurchases. This was in addition to the Company's existing share repurchase program, which had approximately $1.3 billion of remaining authorization at December 31, 2021.

The following information relates to the Company's repurchases of equity securities during each month within the fourth quarter of the fiscal year covered by this report:

At February 8, 2024, there were 4,044 stockholders of record.

General

Marsh & McLennan Companies Inc., and its consolidated subsidiaries (the "Company") is a global professional services firm in the areas of risk, strategy and people. The Company helps clients build the confidence to thrive through the power of perspective of its four market-leading businesses. With annual revenue of $23 billion, the Company has more than 85,000 colleagues advising clients in over 130 countries.

Marsh provides data-driven risk advisory services and insurance solutions to commercial and consumer clients. Guy Carpenter develops advanced risk, reinsurance and capital strategies that help clients grow profitably and pursue emerging opportunities. Mercer delivers advice and technology-driven solutions that help organizations redefine the world of work, reshape retirement and investment outcomes, and unlock health and well-being for a changing workforce. Oliver Wyman Group serves as a critical strategic, economic and brand advisor to private sector and governmental clients. The four businesses also collaborate together to deliver new solutions to help clients manage complex and interconnected risks.

The Company conducts business through two segments:

• Risk and Insurance Services** includes risk management activities (risk advice, risk transfer and risk control and mitigation solutions) as well as insurance and reinsurance broking and services. The Company conducts business in this segment through Marsh and Guy Carpenter.

• Consulting** includes health, wealth and career advice, solutions and products, and specialized management, strategic, economic and brand consulting services. The Company conducts business in this segment through Mercer and Oliver Wyman Group.

The results of operations in the Management Discussion & Analysis ("MD&A") include an overview of the Company’s consolidated 2023 results compared to the 2022 results, and should be read in conjunction with the consolidated financial statements and notes. This section also includes a discussion of the key drivers impacting the Company’s financial results of operations both on a consolidated basis and by reportable segments.

We describe the primary sources of revenue and categories of expense for each segment in the discussion of segment financial results. A reconciliation of segment operating income to total operating income is included in Note 17, Segment Information, in the notes to the consolidated financial statements included in Part II, Item 8, of this report.

For information and comparability of the Company's results of operations and liquidity and capital resources for fiscal year 2021, refer to "Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations" of the Company's Form 10-K for the fiscal year ended December 31, 2022.

This MD&A contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995. Refer to "Information Concerning Forward-Looking Statements" at the outset of this report.

Non-GAAP Measures

The Company reports its financial results in accordance with accounting principles generally accepted in the United States (U.S.), referred to as in accordance with "GAAP" or "reported" results. The Company also refers to and presents a non-GAAP financial measure in non-GAAP revenue, within the meaning of Regulation G and Item 10(e) of Regulation S-K in accordance with the Securities Exchange Act of 1934. The Company has included a reconciliation of this non-GAAP financial measure to the most directly comparable financial measure calculated in accordance with GAAP as part of the consolidated revenue and expense discussion. Percentage changes, referred to as non-GAAP underlying revenue, are calculated by dividing the period over period change in non-GAAP revenue by the prior period non-GAAP revenue.

The Company believes this non-GAAP financial measure provides useful supplemental information that enables investors to better compare the Company’s performance across periods. Management also uses this measure internally to assess the operating performance of its businesses and to decide how to allocate resources. However, investors should not consider this non-GAAP measure in isolation from, or as a substitute for, the financial information that the Company reports in accordance with GAAP. The Company's non-GAAP measure includes adjustments that reflect how management views its businesses and may differ from similarly titled non-GAAP measures presented by other companies.

Financial Highlights

• Consolidated revenue in 2023 was $22.7 billion, an increase of 10%, or 9% on an underlying basis.

• Consolidated operating income increased $1.0 billion, or 23% to $5.3 billion in 2023, compared to 2022. Net income attributable to the Company was $3.8 billion. Earnings per share on a diluted basis increased to $7.53 from $6.04, or 25%, compared with 2022.

• Risk and Insurance Services revenue in 2023 was $14.1 billion, an increase of 11%, on a reported and underlying basis. Operating income was $3.9 billion and $3.1 billion in 2023 and 2022, respectively.

• Consulting revenue in 2023 was $8.7 billion, an increase of 7%, on a reported and underlying basis. Operating income was $1.7 billion and $1.6 billion in 2023 and 2022, respectively.

*•*The Company's results of operations in 2023 were impacted by restructuring activities of $301 million, primarily related to severance and lease exit charges for activities focused on workforce actions, technology rationalization and reductions in real estate.

• The Company completed 14 acquisitions in 2023, the largest being the acquisitions of Honan Insurance Group and Graham Company in the Risk and Insurance Services segment.

• In the Consulting segment, the Company completed the acquisition of Westpac Banking Corporation’s ("Westpac") financial advisory business, Advance Asset Management, and the transfer from Westpac of BT Financial Group's personal and corporate pension funds to the Mercer Super Trust managed by Mercer Australia (referred to collectively, as the "Westpac Transaction").

• In September 2023, the Company issued $600 million of 5.400% senior notes due 2033 and $1.0 billion of 5.700%% senior notes due 2053. In March 2023, the Company issued $600 million of 5.450% senior notes due 2053.

• On October 16, 2023, the Company repaid $250 million of senior notes that matured.

• In 2023, the Company repurchased 6.4 million shares for $1.15 billion.

The macroeconomic and geopolitical environment including multiple major wars, escalating conflict throughout the Middle East and rising tension in the South China Sea, slower GDP growth or recession, lower interest rates, capital markets volatility and inflation has and could continue to potentially impact our business, financial condition, results of operations and cash flows. For more information about these risks, please see “Risk Factors – Macroeconomic Risks” in this annual report on Form 10-K.

For additional details, refer to the Consolidated Results of Operations and Liquidity and Capital Resources sections in this MD&A.

Acquisitions and dispositions impacting the Risk and Insurance Services and Consulting segments are discussed in Note 5, Acquisitions and Dispositions, in the notes to the consolidated financial statements.

Consolidated Results of Operations

Showing the first 8K of 88K characters. Open the full section

Market Risk and Credit Risk

Certain of the Company’s revenues, expenses, assets and liabilities are exposed to the impact of interest rate changes and fluctuations in foreign currency exchange rates and equity markets.

Interest Rate Risk and Credit Risk

Interest income generated from the Company’s cash, cash equivalents, and cash and cash equivalents held in a fiduciary capacity will vary with the general level of interest rates.

The Company had the following investments subject to variable interest rates:

Based on the above balances at December 31, 2023, if short-term interest rates increased or decreased by 10%, or 47 basis points for the year 2024, annual interest income, including interest earned on cash and cash equivalents held in a fiduciary capacity, would increase or decrease by approximately $66 million. At December 31, 2022, a change in short-term interest rates of 10%, or 25 basis points, would have increased or decreased interest income by approximately $30 million. The change in interest rate risk at December 31, 2023 is due to higher short-term interest rates compared to the prior year.

In addition to interest rate risk, our cash investments and fiduciary cash investments are subject to potential loss of value due to counter-party credit risk. To minimize this risk, the Company and its subsidiaries invest pursuant to a Board approved investment policy. The policy mandates the preservation of principal and liquidity and requires broad diversification with counter-party limits assigned based primarily on credit rating and type of investment. The Company carefully monitors its cash, cash equivalents, and cash and cash equivalents held in a fiduciary capacity, and will further restrict the portfolio as appropriate to market conditions. The majority of cash, cash equivalents. and cash and cash equivalents held in a fiduciary capacity are invested in short-term bank deposits and liquid money market funds.

Foreign Currency Risk

The translated values of revenue and expense from the Company’s international operations are subject to fluctuations due to changes in currency exchange rates. The non-U.S. based revenue that is exposed to foreign exchange fluctuations is approximately 53% of total revenue. We periodically use forward contracts and options to limit foreign currency exchange rate exposure on net income and cash flows for specific, clearly defined transactions arising in the ordinary course of business. Although the Company has significant revenue generated in foreign locations which is subject to foreign exchange rate fluctuations, in most cases both the foreign currency revenue and expense are in the functional currency of the foreign location. As such, under normal circumstances, the U.S. dollar translation of both the revenue and expense, as well as the potentially offsetting movements of various currencies against the U.S. dollar, generally tend to mitigate the impact on net operating income of foreign currency risk.

However, there have been periods where the impact was not mitigated due to external market factors, and external macroeconomic events may result in greater foreign exchange rate fluctuations in the future. If foreign exchange rates of major currencies (Euro, British Pound, Australian dollar and Canadian dollar) moved 10% in the same direction against the U.S. dollar compared with the foreign exchange rates in 2023, the Company estimates net operating income would increase or decrease by approximately $80 million. The corresponding increase or decrease in net operating income in 2022 was estimated at $74 million.

The Company has exposure to approximately 80 foreign currencies overall. In Continental Europe, the largest amount of revenue from renewals for the Risk and Insurance Services segment occurs in the first quarter.

Equity Price Risk

The Company holds investments in both public and private companies as well as private equity funds, including investments of approximately $16 million that are valued using readily determinable fair values and approximately $20 million of investments without readily determinable fair values. The Company also has investments of approximately $266 million that are accounted for using the equity method. The Company's investments are subject to risk of decline in market value, which, if determined to be other than temporary, could result in realized impairment losses. The Company periodically reviews the carrying value of such investments to determine if any valuation adjustments are appropriate under the applicable accounting pronouncements.

Other

A number of lawsuits and regulatory proceedings are pending. Refer to Note 16, Claims, Lawsuits and Other Contingencies, in the notes to the consolidated financial statements included in this report.

MARSH & McLENNAN COMPANIES, INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF INCOME

The accompanying notes are an integral part of these consolidated statements.

MARSH & McLENNAN COMPANIES, INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME

The accompanying notes are an integral part of these consolidated statements.

MARSH & McLENNAN COMPANIES, INC. AND SUBSIDIARIES

CONSOLIDATED BALANCE SHEETS

Showing the first 8K of 260K characters. Open the full section

None.

Disclosure Controls and Procedures. Based on their evaluation, as of the end of the period covered by this annual report on Form 10-K, the Company’s chief executive officer and chief financial officer have concluded that the Company’s disclosure controls and procedures (as defined in Rules 13a-15(e) or 15d-15(e) under the Securities Exchange Act of 1934) are effective.

Internal Control over Financial Reporting.

(a)Management’s Annual Report on Internal Control Over Financial Reporting

MANAGEMENT’S ANNUAL REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

The management of Marsh & McLennan Companies, Inc. is responsible for establishing and maintaining adequate internal control over financial reporting for the Company. The Company’s internal control over financial reporting is designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles.

The Company’s internal control over financial reporting includes those policies and procedures relating to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the Company; the recording of all necessary transactions to permit the preparation of the Company’s consolidated financial statements in accordance with generally accepted accounting principles; the proper authorization of receipts and expenditures in accordance with authorizations of the Company’s management and directors; and the prevention or timely detection of the unauthorized acquisition, use or disposition of assets that could have a material effect on the Company’s consolidated financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

Management evaluated the effectiveness of the Company’s internal control over financial reporting as of December 31, 2023 under the supervision and with the participation of the Company’s principal executive and principal financial officers. In making this evaluation, management used the criteria set forth by the Committee of Sponsoring Organizations of the Treadway Commission (COSO) in Internal Control—Integrated Framework issued in 2013. Based on its evaluation, management determined that the Company maintained effective internal control over financial reporting as of December 31, 2023.

Deloitte & Touche LLP, the Independent Registered Public Accounting Firm that audited and reported on the Company’s consolidated financial statements included in this annual report on Form 10-K, also issued an audit report on the effectiveness of the Company’s internal control over financial reporting as of December 31, 2023.

(b)Audit Report of the Registered Public Accounting Firm.

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the Shareholders and the Board of Directors of Marsh & McLennan Companies, Inc.

Opinion on Internal Control over Financial Reporting

We have audited the internal control over financial reporting of Marsh & McLennan Companies, Inc. and subsidiaries (the "Company") as of December 31, 2023, based on criteria established in Internal Control — Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO). In our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2023, based on criteria established in Internal Control — Integrated Framework (2013) issued by COSO.

We have also audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the consolidated financial statements as of and for the year ended December 31, 2023, of the Company and our report dated February 12, 2024, expressed an unqualified opinion on those financial statements.

Basis for Opinion

The Company’s management is responsible for maintaining effective internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting, included in the accompanying Management’s Annual Report on Internal Control Over Financial Reporting. Our responsibility is to express an opinion on the Company’s internal control over financial reporting based on our audit. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audit in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether effective internal control over financial reporting was maintained in all material respects. Our audit included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, testing and evaluating the design and operating effectiveness of internal control based on the assessed risk, and performing such other procedures as we considered necessary in the circumstances. We believe that our audit provides a reasonable basis for our opinion.

Definition and Limitations of Internal Control over Financial Reporting

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

/s/ Deloitte & Touche LLP

New York, New York

February 12, 2024

(c)Changes in Internal Control Over Financial Reporting

There were no changes in the Company’s internal control over financial reporting identified in connection with the evaluation required by Rules 13a-15(d) or 15d-15(d) under the Securities Exchange Act of 1934 that occurred during the quarter ended December 31, 2023 that have materially affected, or are reasonably likely to materially affect, the Company’s internal control over financial reporting.

Rule 10b5-1 Trading Plans

The following Section 16 officers (as defined in Rule 16a-1(f) under the Exchange Act) adopted, modified or terminated "Rule 10b5-1 trading arrangements" (as defined in Item 408 under Regulation S-K of the Exchange Act):

• Paul Beswick, our Senior Vice President and Chief Information Officer, adopted a new trading plan on December 4, 2023. The plan’s maximum length is until December 3, 2024, and first trades will not occur until March 4, 2024, at the earliest. The trading plan is intended to permit Mr. Beswick to (1) sell 1,450 shares, (2) sell up to 8,510 shares subject to performance stock units (" PSUs") and (3) exercise and sell 5,000 stock options.

• Dean Klisura, our President and Chief Executive Officer of Guy Carpenter and Vice Chair, Marsh McLennan, adopted a new trading plan on December 4, 2023. The plan’s maximum length is until December 3, 2024, and first trades will not occur until March 4, 2024, at the earliest. The trading plan is intended to permit Mr. Klisura to (1) sell up to 4,256 shares subject to PSUs, (2) sell 1,419 shares subject to restricted stock units ("RSUs") and (3) exercise and sell 9,994 stock options.

• Mark McGivney, our Chief Financial Officer, adopted a new trading plan on December 4, 2023. The plan’s maximum length is until December 3, 2024, and first trades will not occur until March 4, 2024, at the earliest. The trading plan is intended to permit Mr. McGivney to (1) sell up to 25,526 shares subject to PSUs and (2) exercise and sell 66,393 stock options.

• Stacy Mills, our Vice President and Controller, adopted a new trading plan on December 13, 2023. The plan’s maximum length is until December 12, 2024, and first trades will not occur until March 13, 2024, at the earliest. The trading plan is intended to permit Ms. Mills to (1) sell up to 1,702 shares subject to PSUs, (2) sell 1,572 shares subject to RSUs and (3) exercise and sell 4,101 stock options.

The actual number of shares subject to PSUs that may be sold pursuant to each plan described above is subject to satisfaction of the applicable performance conditions and may vary from the number above.

PART III

Information as to the directors and nominees for the board of directors of the Company is incorporated herein by reference to the material set forth under the heading "Item 1: Election of Directors" in the 2024 Proxy Statement.

The executive officers and executive officer appointees of the Company are Paul Beswick, Katherine J. Brennan, John Q. Doyle, Martine Ferland, Carmen Fernandez, John Jones, Dean Klisura, Mark C. McGivney, Martin South and Nick Studer. Information with respect to these individuals is provided in Part I, Item 1 above under the heading "Executive Officers of the Company".

The information set forth in the 2024 Proxy Statement in the sections "Corporate Governance—Codes of Conduct", "Board of Directors and Committees—Committees—Audit Committee" and "Additional Information—Transactions with Management and Others" is incorporated herein by reference.

The information set forth in the sections "Additional Information—Director Compensation" and "Executive Compensation—Compensation of Executive Officers" in the 2024 Proxy Statement is incorporated herein by reference.

The information set forth in the sections "Additional Information—Stock Ownership of Directors, Management and Certain Beneficial Owners" and "Additional Information—Equity Compensation Plan Information" in the 2024 Proxy Statement is incorporated herein by reference.

The information set forth in the sections "Corporate Governance—Director Independence", "Corporate Governance—Review of Related-Person Transactions" and "Additional Information—Transactions with Management and Others" in the 2024 Proxy Statement is incorporated herein by reference.

The information set forth under the heading "Item 3: Ratification of Selection of Independent Registered Public Accounting Firm—Fees of Independent Registered Public Accounting Firm" in the 2024 Proxy Statement is incorporated herein by reference.

PART IV

The following documents are filed as a part of this report:

(1)Consolidated Financial Statements:

Consolidated Statements of Income for each of the three years in the period ended December 31, 2023

Consolidated Statements of Comprehensive Income for each of the three years in the period ended December 31, 2023

Consolidated Balance Sheets as of December 31, 2023 and 2022

Consolidated Statements of Cash Flows for each of the three years in the period ended December 31, 2023

Consolidated Statements of Shareholders Equity for each of the three years in the period ended December 31, 2023

Notes to Consolidated Financial Statements

Report of Independent Registered Public Accounting Firm

(2)All required Financial Statement Schedules are included in the Consolidated Financial Statements or the Notes to Consolidated Financial Statements.

(3)The following exhibits are filed as a part of this report:

(2.1)Stock Purchase Agreement, dated as of June 6, 2010, by and between Marsh & McLennan Companies, Inc. and Altegrity, Inc. (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2010)

(2.2) Rule 2.7 Announcement, dated as of September 18, 2018 (incorporated by reference to the Company’s Current Report on Form 8-K dated September 18, 2018)

†As permitted by Item 601(b)(4)(iii)(A) of Regulation S-K, the Company has not filed with this Form 10-K certain instruments defining the rights of holders of long-term debt of the Company and its subsidiaries because the total amount of securities authorized under any of such instruments does not exceed 10% of the total assets of the Company and its subsidiaries on a consolidated basis. The Company agrees to furnish a copy of any such agreement to the Commission upon request.

(2.3) Co-operation Agreement, dated as of September 18, 2018, by and among Marsh & McLennan Companies, Inc., MMC Treasury Holdings (UK) Limited and Jardine Lloyd Thompson Group plc. (incorporated by reference to the Company’s Current Report on Form 8-K dated September 18, 2018)

(3.1) Restated Certificate of Incorporation of Marsh & McLennan Companies, Inc. (incorporated by reference to the Company’s Current Report on Form 8-K dated July 17, 2008)

(3.2) Amended and Restated By-Laws of Marsh & McLennan Companies, Inc. (incorporated by reference to the Company’s Current Report on Form 8-K dated January 12, 2017)

(4.1)Indenture dated as of June 14, 1999 between Marsh & McLennan Companies, Inc. and State Street Bank and Trust Company, as trustee (incorporated by reference to the Company’s Registration Statement on Form S-3, Registration No. 333-108566)

(4.2) Third Supplemental Indenture dated as of July 30, 2003 between Marsh & McLennan Companies, Inc. and U.S. Bank National Association (as successor to State Street Bank and Trust Company), as trustee (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2003)

(4.3) Indenture dated as of March 19, 2002 between Marsh & McLennan Companies, Inc. and State Street Bank and Trust Company, as trustee (incorporated by reference to the Company’s Registration Statement on Form S-4, Registration No. 333-87510)

(4.4) Indenture, dated as of July 15, 2011, between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2011)

(4.5) First Supplemental Indenture, dated as of July 15, 2011, between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2011)

(4.6) Form of Third Supplemental Indenture between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to the Company’s Current Report on Form 8-K dated September 24, 2013)

(4.7) Form of Fourth Supplemental Indenture between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to the Company’s Current Report on Form 8-K dated May 27, 2014)

*Management contract or compensatory plan or arrangement required to be filed as an exhibit pursuant to Item 15(b) of Form 10-K.

(4.8) Form of Fifth Supplemental Indenture between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to the Company’s Current Report on Form 8-K dated September 10, 2014)

(4.9) Sixth Supplemental Indenture, dated as of March 6, 2015, between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2015)

(4.10) Seventh Supplemental Indenture, dated as of September 14, 2015, between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to the Company's Current Report on Form 8-K filed on September 14, 2015)

(4.11) Eighth Supplemental Indenture, dated as of March 14, 2016, between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to the Company's Quarterly Report on Form 10-Q filed on May 2, 2016)

(4.12) Ninth Supplemental Indenture, dated as of January 12, 2017, between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to the Company's Annual Report on Form 10-K filed on February 24, 2017)

(4.13) Tenth Supplemental Indenture, dated as of March 1, 2018, between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to the Company's Current Report on Form 8-K filed on March 1, 2018)

(4.14) Eleventh Supplemental Indenture, dated January 15, 2019, between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to the Company's Current Report on Form 8-K filed on January 15, 2019)

(4.15) Twelfth Supplemental Indenture, dated March 21, 2019, between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to the Company's Current Report on Form 8-K filed on March 21, 2019)

(4.16) Thirteenth Supplemental Indenture, dated May 7, 2020, between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to Company’s Current Report on Form 8-K dated May 7, 2020)

(4.17) Fourteenth Supplemental Indenture, dated December 8, 2021, between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as trustee (incorporated by reference to Company’s Current Report on Form 8-K dated December 9, 2021)

*Management contract or compensatory plan or arrangement required to be filed as an exhibit pursuant to Item 15(b) of Form 10-K.

(4.18) Fifteenth Supplemental Indenture, dated October 31, 2022, between Marsh & McLennan Companies, Inc. and the Bank of New York Mellon, as trustee (incorporated by reference to the Company's Current Report on Form 8-K dated October 31, 2022)

(4.19) Sixteenth Supplemental Indenture, dated March 9, 2023, between Marsh & McLennan Companies, Inc. and the Bank of New York Mellon, as trustee (incorporated by reference to the Company's Current Report on Form 8-K dated March 9, 2023)

(4.20) Seventeenth Supplemental Indenture, dated September 11, 2023, between Marsh & McLennan Companies, Inc. and the Bank of New York Mellon, as trustee (incorporated by reference to the Company's Current Report on Form 8-K dated September 11, 2023)

(4.21) Description of Marsh & McLennan Companies, Inc.’s Securities Registered Pursuant to Section 12 of the Securities Exchange Act of 1934 (incorporated by reference to the Company's Annual Report on Form 10-K for the year ended December 31, 2019)

(10.1)*Marsh & McLennan Companies, Inc. U.S. Employee 1996 Cash Bonus Award Voluntary Deferral Plan (incorporated by reference to the Company's Annual Report on Form 10-K for the year ended December 31, 1996)

(10.2)*Marsh & McLennan Companies, Inc. U.S. Employee 1997 Cash Bonus Award Voluntary Deferral Plan (incorporated by reference to the Company's Annual Report on Form 10-K for the year ended December 31, 1997)

(10.3)*Marsh & McLennan Companies, Inc. U.S. Employee 1998 Cash Bonus Award Voluntary Deferral Plan (incorporated by reference to the Company's Annual Report on Form 10-K for the year ended December 31, 1998)

(10.4)*Marsh & McLennan Companies, Inc. 2000 Senior Executive Incentive and Stock Award Plan (incorporated by reference to the Company’s Annual Report on Form 10-K for the year ended December 31, 1999)

(10.5)*Amendments to Marsh & McLennan Companies, Inc. 2000 Senior Executive Incentive and Stock Award Plan and the Marsh & McLennan Companies, Inc. 2000 Employee Incentive and Stock Award Plan (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2005)

(10.6)*Form of 2014 Long-term Incentive Award under the Marsh & McLennan Companies, Inc. 2011 Incentive and Stock Award Plan (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2014)

*Management contract or compensatory plan or arrangement required to be filed as an exhibit pursuant to Item 15(b) of Form 10-K.

(10.7)*Form of 2015 Long-term Incentive Award under the Marsh & McLennan Companies, Inc. 2011 Incentive and Stock Award Plan (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2015)

(10.8)*Form of 2016 Long-term Incentive Award under the Marsh & McLennan Companies, Inc. 2011 Incentive and Stock Award Plan (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2016)

(10.9)*Form of Deferred Stock Unit Award, with grant dates from March 1, 2020 through February 1, 2021, under the Marsh & McLennan Companies, Inc. 2011 Incentive and Stock Award Plan (incorporated by reference to the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2020)

(10.10)*Form of Deferred Stock Unit Award, with grant dates from March 1, 2021 through February 1, 2022, under the Marsh & McLennan Companies, Inc. 2020 Incentive and Stock Award Plan – Cliff Vesting (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2021)

(10.11)*Form of Deferred Stock Unit Award, with grant dates from March 1, 2021 through February 1, 2022, under the Marsh & McLennan Companies, Inc. 2020 Incentive and Stock Award Plan – Ratable Vesting (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2021)

(10.12)*Form of Restricted Stock Unit Award, dated as of February 22, 2021, under the Marsh & McLennan Companies, Inc. 2020 Incentive and Stock Award Plan (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2021)

(10.13)*Form of Performance Stock Unit Award, dated as of February 22, 2021, under the Marsh & McLennan Companies, Inc. 2020 Incentive and Stock Award Plan (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2021)

(10.14)*Form of Stock Option Award, dated as of February 22, 2017, under the Marsh & McLennan Companies, Inc. 2011 Incentive and Stock Award Plan (incorporated by reference to the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2017)

(10.15)*Form of Stock Option Award, dated as of February 21, 2018, under the Marsh & McLennan Companies, Inc. 2011 Incentive and Stock Award Plan (incorporated by reference to the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2018)

*Management contract or compensatory plan or arrangement required to be filed as an exhibit pursuant to Item 15(b) of Form 10-K.

(10.16)*Form of Stock Option Award, dated as of February 19, 2019, under the Marsh & McLennan Companies, Inc. 2011 Incentive and Stock Award Plan (incorporated by reference to the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2019)

(10.17)*Form of Stock Option Award, dated as of May 1, 2019, under the Marsh & McLennan Companies, Inc. 2011 Incentive and Stock Award Plan (incorporated by reference to the Company's Quarterly Report on Form 10-Q for the quarter ended June 30, 2019)

(10.18)*Form of Stock Option Award, dated as of February 19, 2020, under the Marsh & McLennan Companies, Inc. 2011 Incentive and Stock Award Plan (incorporated by reference to the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2020)

(10.19)*Form of Stock Option Award, dated as of February, 22, 2021, under the Marsh & McLennan Companies, Inc. 2020 Incentive and Stock Award (incorporated by reference to the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2021)

(10.20)*Form of Deferred Stock Unit Award, with grant dates from March 1, 2022 through February 1, 2023, under the Marsh & McLennan Companies, Inc. 2020 Incentive and Stock Award Plan – Cliff Vesting (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2022)

(10.21)*Form of Deferred Stock Unit Award, with grant dates from March 1, 2022 through February 1, 2023, under the Marsh & McLennan Companies, Inc. 2020 Incentive and Stock Award Plan – Ratable Vesting (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2022)

(10.22)*Form of Restricted Stock Unit Award, dated as of February 23, 2022, under the Marsh & McLennan Companies, Inc. 2020 Incentive and Stock Award Plan (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2022)

(10.23)*Form of Performance Stock Unit Award, dated as of February 23, 2022, under the Marsh & McLennan Companies, Inc. 2020 Incentive and Stock Award Plan (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2022)

(10.24)*Form of Stock Option Award, dated as of February 23, 2022, under the Marsh & McLennan Companies, Inc. 2020 Incentive and Stock Award Plan (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2022)

*Management contract or compensatory plan or arrangement required to be filed as an exhibit pursuant to Item 15(b) of Form 10-K.

(10.25)*Marsh & McLennan Companies, Inc. 2011 Incentive and Stock Award Plan (incorporated by reference to the Company’s Registration Statement on Form S-8 dated August 5, 2011, Registration No. 333-176084)

(10.26)*Amendment to the Marsh & McLennan Companies, Inc. 2011 Incentive and Stock Award Plan (incorporated by reference to the Company’s Annual Report on Form 10-K for the year ended December 31, 2018)

(10.27)*Marsh & McLennan Companies, Inc. 2020 Incentive and Stock Award Plan (incorporated by reference from Exhibit C to the Company’s Definitive Proxy Statement on Schedule 14A filed on April 3, 2020)

(10.28)2023 Amendment to the Marsh & McLennan Companies, Inc. 2020 Incentive and Stock Award Plan effective January 12, 2023 (incorporated by reference to the Company’s Annual Report on Form 10-K for the year ended December 31, 2022)

(10.29)*Amendments to Certain Marsh & McLennan Companies Equity-Based Awards Due to U.S. Tax Law Changes Affecting Equity-Based Awards granted under the Marsh & McLennan Companies, Inc. 2000 Senior Executive Incentive and Stock Award Plan and the Marsh & McLennan Companies, Inc. 2000 Employee Incentive and Stock Award Plan, effective January 1, 2009 (incorporated by reference to the Company’s Annual Report on Form 10-K for the year ended December 31, 2008)

(10.30)*Section 409A Amendment Document, effective as of January 1, 2009 (incorporated by reference to the Company’s Annual Report on Form 10-K for the year ended December 31, 2008)

(10.31)*Section 409A Amendment Regarding Payments Conditioned Upon Employment-Related Action to Any and All Plans or Arrangements Entered into by the Marsh & McLennan Companies, Inc., or any of its Direct or Indirect Subsidiaries, that Provide for the Payment of Section 409A Nonqualified Deferred Compensation, effective December 21, 2012 (incorporated by reference to the Company’s Annual Report on Form 10-K for the year ended December 31, 2012)

(10.32)*Marsh & McLennan Companies Supplemental Savings & Investment Plan (formerly the Marsh & McLennan Companies Stock Investment Supplemental Plan) Restatement, effective January 1, 2012 (incorporated by reference to the Company’s Annual Report on Form 10-K for the year ended December 31, 2012)

(10.33)*First Amendment to the Marsh & McLennan Companies Supplemental Savings & Investment Plan Restatement effective January 1, 2012 (incorporated by reference to the Company's Annual Report on Form 10-K for the year ended December 31, 2016)

*Management contract or compensatory plan or arrangement required to be filed as an exhibit pursuant to Item 15(b) of Form 10-K.

(10.34)*Second Amendment to the Marsh & McLennan Companies Supplemental Savings & Investment Plan Restatement effective January 1, 2012 (incorporated by reference to the Company's Annual Report on Form 10-K for the year ended December 31, 2017)

(10.35)*Third Amendment to the Marsh & McLennan Companies Supplemental Savings & Investment Plan Restatement effective January 1, 2012 (incorporated by reference to the Company’s Annual Report on Form 10-K for the year ended December 31, 2018)

(10.36)*Fourth Amendment to the Marsh & McLennan Companies Supplemental Savings & Investment Plan Restatement effective January 1, 2012 (incorporated by reference to the Company's Annual Report on Form 10-K for the year ended December 31, 2020)

(10.37)Marsh & McLennan Companies Supplemental Savings & Investment Plan (formerly the Marsh & McLennan Companies Stock Investment Supplemental Plan) Restatement effective January 1, 2022 (incorporated by reference to the Company's Annual Report on Form 10-K for the year ended December 31, 2022)

(10.38)*Marsh & McLennan Companies Benefit Equalization Plan and Marsh & McLennan Companies Supplemental Retirement Plan as Restated, effective January 1, 2012 (incorporated by reference to the Company’s Annual Report on Form 10-K for the year ended December 31, 2012)

(10.39)*First Amendment to the Marsh & McLennan Companies Benefit Equalization Plan and Marsh & McLennan Companies Supplemental Retirement Plan as Restated effective January 1, 2012 (incorporated by reference to the Company's Annual Report on Form 10-K for the year ended December 31, 2016

(10.40)*Second Amendment to the Marsh & McLennan Companies Benefit Equalization Plan and Marsh & McLennan Companies Supplemental Retirement Plan as Restated effective January 1, 2012 (incorporated by reference to the Company's Annual Report on Form 10-K for the year ended December 31, 2016)

(10.41)*Marsh & McLennan Companies, Inc. Senior Executive Severance Pay Plan (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the Quarter ended March 31, 2008)

(10.42)*Amendment to the Marsh & McLennan Companies, Inc. Senior Executive Severance Pay Plan, effective December 31, 2009 (incorporated by reference to the Company’s Annual Report on Form 10-K for the year ended December 31, 2009)

(10.43)*Marsh & McLennan Companies, Inc. Senior Management Incentive Compensation Plan (incorporated by reference to the Company’s Annual Report on Form 10-K for the year ended December 31, 1994)

*Management contract or compensatory plan or arrangement required to be filed as an exhibit pursuant to Item 15(b) of Form 10-K.

(10.44)*Marsh & McLennan Companies, Inc. Directors' Stock Compensation Plan - May 31, 2009 Restatement (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2009)

(10.45)*Marsh & McLennan Companies International Retirement Plan As Amended and Restated Effective January 1, 2009 (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2014)

(10.46)*Description of compensation arrangements for independent directors of Marsh & McLennan Companies, Inc. effective June 1, 2023 (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2023)

(10.47)*Letter Agreement, effective as of March 20, 2013, between Marsh & McLennan Companies, Inc. and Daniel S. Glaser (incorporated by reference to the Company's Quarterly Report on Form 10-Q for the quarter ended September 30, 2013)

(10.48)*Non-Competition and Non-Solicitation Agreement, effective as of September 18, 2013, between Marsh & McLennan Companies, Inc. and Daniel S. Glaser (incorporated by reference to the Company's Quarterly Report on Form 10-Q for the quarter ended September 30, 2013)

(10.49)*Letter Agreement, effective as of May 14, 2014, between Marsh & McLennan Companies, Inc. and Daniel S. Glaser (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2014)

(10.50)*Letter Agreement, effective as of February 22, 2016, between Marsh & McLennan Companies, Inc. and Daniel S. Glaser (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2016)

(10.51)*Letter Agreement, effective as of February 22, 2017, between Marsh & McLennan Companies, Inc. and Daniel S. Glaser (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2017)

(10.52)*Letter Agreement, dated as of September 18, 2019, between Marsh & McLennan Companies, Inc. and Daniel S. Glaser (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2019)

(10.53)*Letter Agreement Amendment, dated September 23, 2022, between Marsh & McLennan Companies, Inc. and Daniel S. Glaser (incorporated by reference to the Company’s Current Report on Form 8-K dated September 23, 2022)

(10.54)*Letter Agreement, effective as of January 1, 2016, between Marsh & McLennan Companies, Inc. and Mark C. McGivney (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2015)

*Management contract or compensatory plan or arrangement required to be filed as an exhibit pursuant to Item 15(b) of Form 10-K.

(10.55)*Non-Competition and Non-Solicitation Agreement, effective as of January 1, 2016, between Marsh & McLennan Companies, Inc. and Mark C. McGivney (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2015)

(10.56)*Letter Agreement, effective as of January 17, 2018, between Marsh & McLennan Companies, Inc. and Mark C. McGivney (incorporated by reference to the Company's Annual Report on Form 10-K for the year ended December 31, 2017)

(10.57)*Letter Agreement, effective as of January 16, 2019, between Marsh & McLennan Companies, Inc. and Mark C. McGivney (incorporated by reference to the Company’s Annual Report on Form 10-K for the year ended December 31, 2018)

(10.58)*Letter Agreement, effective as of September 22, 2022, between Marsh & McLennan Companies, Inc. and Mark C. McGivney (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2022)

(10.59)*Letter Agreement, effective as of July 5, 2017, between Marsh & McLennan Companies, Inc. and John Q. Doyle (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2018)

(10.60)*Non-Competition and Non-Solicitation Agreement, dated as of February 25, 2016, between Marsh & McLennan Companies, Inc. and John Q. Doyle (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2018)

(10.61)*Letter Agreement, effective as of January 15, 2020, between Marsh & McLennan Companies, Inc. and John Q. Doyle (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2020)

(10.62)*Letter Agreement, effective as of January 1, 2022 between Marsh & McLennan Companies, Inc. and John Q. Doyle (incorporated by reference to the Company's Annual Report on Form 10-K for the year ended December 31, 2021)

(10.63)*Letter Amendment, dated November 10, 2022, between Marsh & McLennan Companies, Inc. and John Q. Doyle (incorporated by reference to the Company's Current Report on Form 8-K/A dated September 26, 2022)

(10.64)*Letter Agreement, effective as of March 1, 2019, between Marsh & McLennan Companies, Inc. and Martine Ferland (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2020)

(10.65)*Non-Competition and Non-Solicitation Agreement, effective as of March 1, 2016, between Marsh & McLennan Companies, Inc. and Martine Ferland (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2020)

*Management contract or compensatory plan or arrangement required to be filed as an exhibit pursuant to Item 15(b) of Form 10-K.

(10.66)*Letter Agreement, effective as of January 20, 2021, between Marsh & McLennan Companies, Inc. and Martine Ferland (incorporated by reference to the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2021)

(10.67)*Letter Agreement, effective as of April 1, 2022, between Marsh & McLennan Companies, Inc. and Martine Ferland (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2022)

(10.68)*Letter Agreement, effective as of January 1, 2022, between Marsh & McLennan Companies, Inc. and Martin South (incorporated by reference to the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2023)

(10.69)*Non-Competition and Non-Solicitation Agreement, dated as of December 1, 2021, between Marsh & McLennan Companies, Inc. and Martin South (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2023)

(10.70)*Letter Agreement, effective as of January 1, 2022, between Marsh & McLennan Companies, Inc. and Peter C. Hearn (incorporated by reference to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2022)

(10.71)Paying Agency Agreement, dated as of March 21, 2019, between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, London Branch, as paying agent (incorporated by reference to the Company's Current Report on Form 8-K filed on March 21, 2019)

(10.72)Shareholder Undertaking, dated as of September 18, 2018 (incorporated by reference to the Company’s Current Report on Form 8-K dated September 18, 2018)

(10.73)Form of Director Undertaking, dated as of September 18, 2018 (incorporated by reference to the Company’s Current Report on Form 8-K dated September 18, 2018)

(10.74)Bridge Loan Agreement, dated as of September 18, 2018 by and between Marsh & McLennan Companies, Inc., the lenders party thereto and Goldman Sachs Bank USA, as administrative agent (incorporated by reference to the Company’s Current Report on Form 8-K dated September 18, 2018)

(10.75)Calculation Agency Agreement, dated as of January 15, 2019, between Marsh & McLennan Companies, Inc. and The Bank of New York Mellon, as calculation agent (incorporated by reference to the Company's Current Report on Form 8-K filed on January 15, 2019)

*Management contract or compensatory plan or arrangement required to be filed as an exhibit pursuant to Item 15(b) of Form 10-K.

(10.76)Amended and Restated 5 Year Credit Agreement, dated as of October 11, 2023 among Marsh & McLennan Companies, Inc., the designated subsidiaries as party thereto as borrowers, Citibank, N.A., as administrative agent, and the lenders from time to time party thereto (incorporated by reference to the Company's Quarterly Report on Form 10-Q for the quarter ended September 30, 2023)

(14.1)Code of Ethics for Chief Executive and Senior Financial Officers (incorporated by reference to the Company’s Annual Report on Form 10-K for the year ended December 31, 2002)

(21.1)List of Subsidiaries of Marsh & McLennan Companies, Inc.

(23.1)Consent of Independent Registered Public Accounting Firm

(24.1)Power of Attorney (included on signature page)

(31.1)Rule 13a-14(a)/15d-14(a) Certification of Chief Executive Officer

(31.2)Rule 13a-14(a)/15d-14(a) Certification of Chief Financial Officer

(32.1)Section 1350 Certifications

(97.1) Marsh & McLennan Companies, Inc. Compensation Clawback Policy dated as of December 1, 2023.

101.INSXBRL Instance Document

101.SCHXBRL Taxonomy Extension Schema

101.CALXBRL Taxonomy Extension Calculation Linkbase

101.DEFXBRL Taxonomy Extension Definition Linkbase

101.LABXBRL Taxonomy Extension Label Linkbase

101.PREXBRL Taxonomy Extension Presentation Linkbase

104.Cover Page Interactive Data File (formatted as inline XBRL and contained in Exhibit 101)

None.

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Each person whose signature appears below hereby constitutes and appoints Courtenay Birchler and Connor Kuratek, and each of them singly, such person’s lawful attorneys-in-fact and agents, with full power to them and each of them to sign for such person, in the capacity indicated below, any and all amendments to this Annual Report on Form 10-K filed with the Securities and Exchange Commission.

Pursuant to the requirements of the Securities Exchange Act of 1934, this report has been signed below by the following persons on behalf of the registrant and in the capacities indicated this 12th day of February, 2024.