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 McLennan Agency?
Marsh McLennan Agency provides business insurance and employee health and benefits, alongside retirement, wealth, and private-client services across the United States and Canada. Its US small-business page lists six common coverage types and directs buyers to request a personalized quote by phone; the insurer and terms for a specific placement must be confirmed in the proposal. 4,5
Read the Marsh McLennan Agency profile
Read the Marsh McLennan Agency Professional Liability (E&O) Insurance page
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. 7,8,9,10
Key Differences in Professional Liability (E&O) Insurance
Professional Class and Product Scope
Aon describes professional liability as coverage tailored to a firm’s needs and names law, accounting and consulting among the firms served. Marsh McLennan Agency lists E&O and specialist lines such as architects-and-engineers and lawyers professional liability, while clarifying that the overview does not treat them as one form. A buyer should identify the correct occupational product rather than assume a general E&O policy covers licensed work; ask each provider how the insured-services definition is written. 3 6
Placement Detail and Buyer Decisions
Marsh McLennan Agency invites organizations to discuss placement with an adviser or specialist but does not set a universal limit or retention. Aon also describes advisor-led brokerage and does not publish policy terms or identify the carrier for a particular placement. The route is consultative in both cases, so compare the actual proposed form, not the product labels. Request the insurer, exclusions, limits and retroactive date for the policy matched to your profession. 3 6
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 McLennan Agency
Review Score
2 rated sources
There are almost no public customer reviews of Marsh McLennan Agency (MMA). Trustpilot shows 3.2 out of 5, but from a single review, and BBB shows an A grade with four complaints closed in three years.[8][9][1]
Read Marsh McLennan Agency reviewsOffering Details
Aon vs Marsh McLennan Agency: Professional Liability (E&O) Insurance: documented features by provider
| Criteria | Aon Professional Liability / E&O brokerage and risk-advisory offering | Marsh McLennan Agency professional errors omissions (official overview) |
|---|---|---|
| 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 McLennan Agency describes arranging professional errors omissions for the audience stated on the cited product page. 6Company-reported. professional errors omissions marketed by marsh-mclennan-agency; scope is limited to the cited official product overview and described audience. This is not a policy form or a universal eligibility statement. |
| 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. | Confirm in your quote. |
| 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. | Organizations seeking professional liability placement; source does not imply all professions share one policy. 6Company-reported. professional errors omissions marketed by marsh-mclennan-agency; scope is limited to the cited official product overview and described audience. This is not a policy form or a universal eligibility statement. |
| 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. | The cited product page describes E&O and named specialist professional lines, including architects and engineers and lawyers professional liability; the overview does not treat them as one form. Marketing description only; actual coverage, exclusions, conditions, limits, and availability depend on the issued policy and jurisdiction. 6Company-reported. professional errors omissions marketed by marsh-mclennan-agency; scope is limited to the cited official product overview and described audience. This is not a policy form or a universal eligibility statement. |
| 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. | The cited overview does not set a universal limit or retention for this line. Ask for the proposed policy form, limits, retentions, exclusions, and conditions in the quote. 6Not publicly disclosed. Only the cited marketing page was reviewed for published limit and retention information; no policy-form entitlement is inferred. |
| 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. | Confirm in your quote. |
| How to Apply | Confirm in your quote. | The page invites organizations to contact a Marsh McLennan Agency adviser or specialist to discuss placement. The page does not establish a quote, bind, or coverage-effective timeline. 6Company-reported. professional errors omissions marketed by marsh-mclennan-agency; scope is limited to the cited official product overview and described audience. This is not a policy form or a universal eligibility statement. |
Full Comparison
More Aon vs Marsh McLennan Agency 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 McLennan Agency
- Who We Are. Marsh McLennan Agency; Lines 193-195: ‘a business of Marsh’ and company-listed service lines across US and Canada. This does not establish the legal entity for an account, corporate ownership chart, or insurer role. Accessed 2026-09-29.
- Small Business Insurance Solutions. Marsh McLennan Agency; Lines 205-207: small-business audience and call invitation; lines 224-249 list six coverage categories and short descriptions; line 264 is an embedded form whose function is not stated. No form submitted. Accessed 2026-09-29.
- Executive and Professional Liability | MMA. Marsh McLennan Agency; E&O, architects and engineers, and lawyers professional lines are named in the policy suite. Accessed 2026-09-30.
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.
