Aon vs 
Marsh: How Do They Compare for Professional Liability (E&O) Insurance?
What Is Aon?
Aon’s U.S. Commercial Risk terms describe brokerage for certain insurance programs, while its Middle Market page describes a dedicated practice for mid-sized organizations across North America. The public materials reviewed do not identify the licensed producer or insurer for a particular placement. Ask which entity will produce each line and which insurer will issue the policy; request jurisdiction details for the proposed placement and ask how compensation and claim notice work for your account. 1,2
What Is Marsh?
Marsh suits technology and larger businesses seeking specialist cyber placement or broad global risk advice; small firms wanting a quick standard quote should compare its MMA route or digital agencies. 4,5,6,7
What Is Professional Errors and Omissions (E&O) Insurance?
Professional liability can help pay defense costs and covered losses when a client says your advice or service caused financial harm. If customers rely on your work, list every service you provide and check the claims-made reporting and prior-work terms. 10,11,12,13
Key Differences in Professional Liability (E&O) Insurance
Professional Class and Product Scope
Aon says it tailors professional-liability structures for professional-services firms, but does not list coverage features on its practice overview. Marsh says E&O can respond to liability and defense costs for alleged errors, omissions or negligence in professional services; it adds that many policies also cover privacy violations and computer-security breaches. A buyer with blended professional and technology exposure should ask whether those extensions are actually in the Marsh form and compare them with Aon’s proposed wording. 3 8
Placement Detail and Buyer Decisions
Marsh names specialized fields including banking, venture capital, accounting, law, architecture, media, technology and healthcare, and says it uses attorneys, economists and actuaries alongside coverage specialists to assess exposures. Aon’s listed audience is law, accounting and consulting firms, with advisors using data and industry knowledge. Neither record names the carrier or publishes limits. Confirm the insurer, insured services definition and any cyber sublimit before treating the descriptions as comparable. 3 8
What to Confirm in Professional Liability (E&O) Insurance Quotes
Review Scores
These averages can combine ratings for different products, locations, and customer groups, including approximate BBB grade conversions. Read each review for the sources, scope, and calculation.
Aon
Review Score
3 rated sources
Public ratings for Aon are low: Trustpilot shows 1.2 out of 5 from 782 reviews, and BBB shows 1.6 from five. Aon is a global firm, so those pages mostly reflect other parts of the business, not large U.S. commercial accounts.[4][6][7]
Read Aon reviewsMarsh
Review Score
2 rated sources
Marsh’s global Trustpilot profile has a poor 1.3/5 score. Treat it as a service warning to investigate with your proposed team; it does not isolate US commercial accounts.[2][4][7]
Read Marsh reviewsOffering Details
Aon vs Marsh: Professional Liability (E&O) Insurance: documented features by provider
| Criteria | Aon Professional Liability / E&O brokerage and risk-advisory offering | Marsh Professional Liability Insurance Brokerage |
|---|---|---|
| Role in This Line | Aon presents Professional Liability / E&O as a line its Professional Services Practice helps arrange or advise on for professional-service firms. Aon is describing a global brokerage and advisory service, not issuing the underlying policy. The producing legal entity and carrier for any particular placement are not named on this page. 3Company-reported. Aon’s global professional-services practice page. This establishes a marketed brokerage/advisory offering, not policy issuance or account-specific placement. | Marsh's financial and professional liability practice places professional liability (errors and omissions) insurance; MMA also places E&O coverage within its executive and professional liability practice for middle-market clients. 8,9Company-reported. Marsh professional liability page and MMA executive and professional liability page. |
| Issuing Insurer | The reviewed practice page does not name the insurer or producing legal entity for a specific placement. Ask for both on the quote and binder. 3Not found in reviewed sources. Aon’s global practice page as reviewed 2026-09-30; no state-specific placement schedule or buyer quote was reviewed. This does not establish that Aon cannot arrange a placement. | The reviewed pages do not name a specific professional liability insurer. 8,9Not publicly disclosed. Marsh professional liability page and MMA executive and professional liability page as read on 2026-09-23. |
| Who It’s For | Aon identifies law, accounting and consulting firms as the audience for its global Professional Services Practice. That audience scope does not establish eligibility for every firm or other business. 3Company-reported. Audience described for Aon’s global professional-services practice. It does not establish U.S. state availability or underwriting eligibility for a placement. | Marsh names specialized industries its professional liability experts serve, including banking and broker/dealers, insurance companies and asset managers, merchant banking and venture capital, accountants, attorneys, architects and engineers, media and entertainment, technology, and healthcare and biotechnology. 8Company-reported. Marsh professional liability page, What We Offer section. |
| Coverage Features | Aon describes professional liability as addressing professional-services firms’ liability exposure and says it tailors coverage structures to a firm’s needs. It identifies E&O as a commonly used name for professional-liability insurance; actual policy terms are not stated. 3Company-reported. Aon’s marketing description of the brokerage/coverage area. The page is not the insurer’s policy form and does not establish an insured's entitlement to coverage. | Marsh says professional liability coverage can protect a company against liability and defense costs from a claim alleging an error, omission or negligence in performing professional services, and that many policies also cover privacy violations and computer security breaches. 8Company-reported. Marsh professional liability page opening description; illustrative policy description, not a specific policy form. |
| Limits and Retentions | The reviewed page does not state a buyer-specific limit, retention, deductible or other placement terms. Confirm these in the quote, bond or issued policy. 3Not publicly disclosed. Aon’s global practice page as reviewed 2026-09-30; no quote, bond form or issued policy was reviewed. | Confirm in your quote. |
| Risk Services | Aon says its professional-services advisors use industry knowledge, insights, data and tools to support risk-management and human-capital decisions. This is a company-described advisory service, not a claim outcome or policy benefit. 3Company-reported. Company-reported advisory services on Aon’s global practice page; account-specific service scope is not stated. | Marsh says it employs attorneys, economists and actuaries alongside coverage specialists to assess a client's professional liability exposure from multiple angles, given the complexity of these risks. 8Company-reported. Marsh professional liability page. |
Full Comparison
More Aon vs Marsh Comparisons
Other Professional Liability (E&O) Insurance Comparisons
Sources
Aon
- Commercial Risk Solutions U.S. Brokerage Terms of Service. Aon; Lines 120–127: certain-program broker-of-record scope, consultation, application assistance, client signature and bind instruction, and account administration; lines 140–147: variable and contingent compensation, potential placement incentive, and client request route; lines 206–213: no price guarantee and surplus-lines limitations; lines 229–231: client insurer-notice duty unless separately agreed. Accessed 2026-09-29.
- Middle Market Clients. Aon; Lines 125–132: mid-sized organizations and middle-market framing; lines 165–173: dedicated practice and North America statement; lines 188–224: Commercial Risk capabilities. No numeric company-size cutoff or U.S.-only eligibility rule is stated on the reviewed page. Accessed 2026-09-29.
- Professional Services Practice. Aon; Named professional-services audiences and global advisory role, lines 125–128; line offerings and explanations lines 131–190; contact link lines 120–122. Global practice page; no U.S. state or account-specific placement schedule. Accessed 2026-09-30.
Marsh
- Marsh | Leader in risk, strategy, people, and investments. Marsh; Hero and capability tiles; FAQ: What does Marsh do?; industries served; Is Marsh the same as Marsh McLennan? January 2026 brand change. Accessed 2026-09-16.
- Compensation guide for US clients. Marsh; US broking segments; broker role; retail commissions, client fees, wholesale, insurer consulting, contingent and supplemental commissions; Marsh LLC and Marsh USA LLC; page 3: broker role and Marsh & McLennan Agency segment; page 7: copyright © 2024 Marsh LLC. Accessed 2026-09-16.
- Marsh McLennan Agency (MMA). Marsh; Middle-market US organizations; wholly-owned subsidiary; business insurance, employee health and benefits, retirement, private client. Accessed 2026-09-16.
- Technology | Insurance Broking & Risk Management. Marsh; Opening Technology Practice description; practice links including data center insurance, fintech and Stratus; Talk to us. Accessed 2026-09-16.
- Professional liability. Marsh; Opening description; What We Offer: specialized industries served (banking, insurance/asset managers, merchant banking/venture capital, accountants/attorneys/architects/engineers, media/communications/entertainment, technology, healthcare/biotechnology). Accessed 2026-09-23.
- Expert Executive and Professional Liability Insurance. Marsh McLennan Agency; Our policies include D&O, E&O, EPL, commercial crime/fidelity, network security privacy risk/cyber, fiduciary, media liability, IP, architects and engineers, lawyers professional, and kidnap and ransom. Accessed 2026-09-23.
Professional Liability (E&O) Insurance Guide
- FAQ: Professional liability insurance. Texas Department of Insurance; What’s professional liability coverage?; What types of damages…; What’s general liability insurance?; Do I need professional liability… if I have general liability…?; Is professional liability insurance required?; Can a client require…?; What’s the difference between occurrence policies and claims-made policies. Accessed 2026-09-16.
- Professional liability insurance. Insurance Information Institute; Opening paragraphs (professional services/advice and E&O name); Claims not covered by general liability; What types of businesses need professional liability insurance?; What’s covered… and what’s not (claims-made versus occurrence, defense and judgments, non-financial/intentional limits, BOP/in-home exclusion). Accessed 2026-09-16.
- Get business insurance. U.S. Small Business Administration; Six common types of business insurance table. Accessed 2026-09-16.
- Professional Liability – US Direct Errors and Omissions Insurance. Hiscox Inc. specimen; About this Policy / Coverage for Claims Made Against You; I.A Insuring Agreement; I.B Defense; I.C Settlement; II.A Notice of Claims; II.C Optional Extended Reporting Period; III.A, III.K, III.M, III.R, III.S Exclusions; IV.A–B Limits and Deductible; VI.O Professional Services; VI.U Wrongful Act. Accessed 2026-09-16.
