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    Best Auditing Firms for USA Clients in 2026

    Review leading auditing firms serving USA clients, with company profiles that explain each provider's expertise, delivery focus and fit.

    Use the comparison to build a shortlist, then review each company profile for its specialty, location and approach.

    Updated October 10, 2026

    Auditing Firms Comparison Table 2026

    Side-by-side comparison of leading providers serving USA clients

    CompanySpecialtyLocationWebsite
    #1DeloitteLargest of the Big Four by total revenue at $70.5 billion FY2025.London, United KingdomVisit site
    #2PwC (PricewaterhouseCoopers)Second-largest Big Four firm, auditing a large share of the Fortune Global 500 alongside its advisory and tax practices.London, United KingdomVisit site
    #3EY (Ernst & Young)Big Four firm with global assurance practice, reporting $24.15 billion total revenue for 2025.London, United KingdomVisit site
    #4KPMGFourth Big Four firm, valued at $15.20 billion in 2025, with audit as a core service line alongside tax and advisory.Amstelveen, NetherlandsVisit site
    #5RSM US LLPLargest US firm outside the Big Four, with a substantial middle-market assurance practice.Chicago, IL, USAVisit site
    #6BDO USAMid-market firm providing assurance services alongside tax and advisory, with FY2025 revenue of $3.018 billion.Chicago, IL, USAVisit site
    #7Grant ThorntonFounded 1924, providing audit and assurance to middle-market and growth companies.Chicago, IL, USAVisit site
    #8Baker TillyTop-ten US firm providing audit and assurance alongside tax and advisory to middle-market organizations.Chicago, IL, USAVisit site
    #9Forvis MazarsTop-ten US firm providing assurance services, formed from the combination of Forvis and Mazars.Springfield, MO, USAVisit site
    #10CBIZ / Mayer Hoffman McCannCBIZ provides accounting services with attest and audit work performed by its affiliate Mayer Hoffman McCann under a separate structure.Cleveland, OH, USAVisit site

    Use this comparison to identify a shortlist, then review the detailed company profiles and USA buyer’s guide below.

    Detailed Auditing company profiles

    Review the available information for each provider before requesting references, pricing and a project proposal.

    1.Deloitte

    London, United Kingdom

    Largest of the Big Four by total revenue at $70.5 billion FY2025. Audit and assurance is one of its core service lines, covering statutory audit for listed and private companies globally.

    Visit website →

    2.PwC (PricewaterhouseCoopers)

    London, United Kingdom

    Second-largest Big Four firm, auditing a large share of the Fortune Global 500 alongside its advisory and tax practices.

    Visit website →

    3.EY (Ernst & Young)

    London, United Kingdom

    Big Four firm with global assurance practice, reporting $24.15 billion total revenue for 2025.

    Visit website →

    4.KPMG

    Amstelveen, Netherlands

    Fourth Big Four firm, valued at $15.20 billion in 2025, with audit as a core service line alongside tax and advisory.

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    5.RSM US LLP

    Chicago, IL, USA

    Largest US firm outside the Big Four, with a substantial middle-market assurance practice.

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    6.BDO USA

    Chicago, IL, USA

    Mid-market firm providing assurance services alongside tax and advisory, with FY2025 revenue of $3.018 billion.

    Visit website →

    7.Grant Thornton

    Chicago, IL, USA

    Founded 1924, providing audit and assurance to middle-market and growth companies.

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    8.Baker Tilly

    Chicago, IL, USA

    Top-ten US firm providing audit and assurance alongside tax and advisory to middle-market organizations.

    Visit website →

    9.Forvis Mazars

    Springfield, MO, USA

    Top-ten US firm providing assurance services, formed from the combination of Forvis and Mazars.

    Visit website →

    10.CBIZ / Mayer Hoffman McCann

    Cleveland, OH, USA

    CBIZ provides accounting services with attest and audit work performed by its affiliate Mayer Hoffman McCann under a separate structure.

    Visit website →
    USA Buyer’s Guide

    How to choose the best Auditing Firms

    Compare delivery models, rates, contracts and risk before selecting a provider for a US engagement.

    01

    How we shortlist Auditing Firms firms for US clients

    This page lists 10 auditing firms providers that work with United States clients. We look at delivery track record, whether the team overlaps with US time zones, how they scope and price work, and whether they can sign standard US contracts including an MSA, SOW, NDA and mutual indemnity.

    Firms currently featured include Deloitte, PwC (PricewaterhouseCoopers), EY (Ernst & Young), and KPMG.

    Delivery footprints on this list span London, United Kingdom, Amstelveen, Netherlands, Chicago, IL, USA, and Springfield, MO, USA, so you can choose between onshore US delivery, nearshore teams with 3–5 hours of overlap, and offshore teams priced for volume work.

    02

    Auditing Firms rates and engagement models in the US

    US buyers usually see three engagement models for auditing firms: fixed-scope projects, time and materials with a monthly cap, and a dedicated team retainer. Onshore US consultancies typically bill $121–$250 per hour, nearshore partners in Latin America $55–$95, and offshore teams $25–$55.

    Ask for a rate card by role, not a blended rate — a blended number hides how much of the work is done by junior staff. For fixed-bid work, insist on a written change-order process, and for retainers, confirm the notice period and any minimum monthly hours.

    Watch the total cost of ownership: discovery workshops, knowledge transfer, post-launch support, and the cost of taking the work back in house at the end.

    03

    Contracts, compliance and risk for US engagements

    Before you sign, confirm the provider carries professional liability (E&O) and cyber insurance with US-acceptable limits, and that the MSA clearly assigns IP ownership of all deliverables to you on payment.

    If the engagement touches regulated data, get the compliance posture in writing: SOC 2 Type II for the provider's own systems, HIPAA with a signed BAA for health data, CCPA/CPRA handling for California consumer data, GLBA for financial services, and background-check policies for anyone with production access.

    Also nail down worker classification and subcontracting — many US buyers require written approval before any part of the work is passed to a third party.

    04

    Questions to ask every auditing firms provider

    • Who exactly will do the work, and can we interview them before the SOW is signed?
    • Show two references from US clients of our size in the last 18 months.
    • What is your escalation path, and what hours does your team overlap with ours?
    • How is scope change handled — hourly, change order, or absorbed?
    • What does handover look like if we end the engagement in 90 days?
    • Which parts of delivery are subcontracted, and to whom?

    Run the same questions past two or three firms from this list and compare the answers side by side — the differences are usually more revealing than the proposals.

    FAQ

    Frequently asked questions about Auditing Firms

    Practical answers for USA clients comparing providers, pricing and engagement models.

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