DisclosureIndependent directory. Not a CPA firm. Nothing here is legal, audit, or tax advice. Methodology.
Most experienced SOC 2 audit firms: 10 firms ranked by SOC reporting history
Ten SOC 2 audit firms ranked by how long they have done SOC and SAS 70 service-auditor work, using dated public sources. The AICPA's SOC 1, SOC 2 and SOC 3 reports replaced SAS 70 service-auditor reports for reports on or after June 15, 2011 (ISACA Journal, March 1, 2011: https://www.isaca.org/resources/isaca-journal/past-issues/2011/understanding-the-new-soc-reports), so 15 years of SOC reporting means working since the framework began; many firms did SAS 70 work before that. Experience is one factor, not a guarantee of audit quality.
How we picked: Ten SOC 2 audit firms ranked by how long they have done SOC and SAS 70 service-auditor work, using dated public sources. The AICPA's SOC 1, SOC 2 and SOC 3 reports replaced SAS 70 service-auditor reports for reports on or after June 15, 2011 (ISACA Journal, March 1, 2011: https://www.isaca.org/resources/isaca-journal/past-issues/2011/understanding-the-new-soc-reports), so 15 years of SOC reporting means working since the framework began; many firms did SAS 70 work before that. Experience is one factor, not a guarantee of audit quality.
Positions 1 to 3 are an editorial ranking of specialist firms whose business began in service-auditor work; each entry shows its evidence. Positions 4 to 10 come from the 20 audit firms in this directory and are ordered by the earliest dated public evidence we could fetch of the firm performing SAS 70 or SOC examinations (a client release, a public-body record, or the firm's own dated history). Those dates are lower bounds: large firms' SAS 70 practices very likely predate the earliest record we found, so read the order as "verified at least since", not as a precise age. A long track record does not replace checking a firm's AICPA peer review, the team assigned to you, and its experience in your industry. Sources were checked on 2026-11-04 and are cited inline as URLs.
Schellman
Best for: Buyers who want a firm that started as a SAS 70 specialist in 2002
Founded in 2002 as "a two-person company focused solely on SAS 70 examinations", the service-auditor report that SOC reports replaced: about 24 years of service-auditor work, and SOC reports since their 2011 start (Schellman, May 2, 2022: https://www.schellman.com/blog/news/shaping-compliance-for-20-years).
A 2006 CPA Practice Advisor profile describes SAS 70 Solutions, a Tampa firm founded in 2002 by Christopher Schellman and Scott Price, as the first firm to specialize exclusively in SAS 70 audits (https://www.cpapracticeadvisor.com/?p=4351).
Self-reported scale: more than 2,000 SOC reports a year, and on April 30, 2026 the first assessor to assess 200 cloud offerings on the FedRAMP Marketplace (Schellman press release: https://www.schellman.com/blog/news/schellman-reaches-200-fedramp-assessed-offerings).
AICPA peer review status is listed as unknown in our data; check the AICPA public file before engaging (Schellman profile).
Pricing: No public price; quotes are scoped
A-LIGN
Best for: Buyers who want a high-volume SOC specialist with roots in SAS 70 audits
Founded in 2009 (A-LIGN: https://www.a-lign.com/ai.html). Accounting Today reported the new Tampa firm, then A-lign CPA, on November 12, 2009, with SAS 70 audits among its planned services: about 17 years of service-auditor work, and SOC reports since 2011 (https://www.accountingtoday.com/news/new-cpa-firm-formed-in-tampa).
Founder and CEO Scott Price founded SAS 70 Solutions and was its president until 2009 (FSU Foundation: https://foundation.fsu.edu/directory/scott-g-price).
Self-reported scale: about 200 dedicated SOC auditors (https://www.a-lign.com/ai.html), 36k+ completed audits and six listed office locations (https://www.a-lign.com/about).
AICPA peer review status is listed as unknown in our data (A-LIGN profile).
Pricing: No public price; quotes are scoped
360 Advanced
Best for: Buyers who want one firm for SOC, ISO, HITRUST, PCI and FedRAMP work
Founded in 2004, per the firm's February 4, 2026 PR Newswire release (syndicated copy: https://smb.orangeleader.com/article/360-ADVANCED-EXPANDS-PRIVACY-ASSURANCE-SERVICES-WITH-ISOIEC-27701-ACCREDITATION/6983ec69513d4aa348230a73); its homepage cites "20+ Years" and 900+ clients (https://360advanced.com/). Some third-party profiles give 2009 or 2010 instead.
Attest work is performed by 360 Advanced, Inc., a licensed Florida CPA firm registered with the PCAOB (https://360advanced.com/who-we-are/).
AICPA peer review: pass, per our data (360 Advanced profile).
Pricing: No public price; quotes are scoped
EY (Ernst & Young)
Best for: Enterprises that want a Big Four firm with a long public SAS 70 record
Verified since at least 2000: Ernst & Young LLP performed the SAS 70 Type II examination of the NIH Center for Information Technology's data center for October 1, 2000 to September 30, 2001 (NIH CIT Interface No. 221, December 17, 2001, archived: https://webarchive.library.unt.edu/web/20090506102732mp_/http://datacenter.cit.nih.gov/interface/interface221/audit.html).
Engaged again for the NIH examination in July to September 2002 (Interface No. 225, December 20, 2002, archived: https://webarchive.library.unt.edu/web/20130216135646mp_/http://datacenter.cit.nih.gov/interface/interface225/audit02.html).
Best for: Enterprises that want a Big Four firm for SOC plus FedRAMP work
Verified since at least 2001: the NYISO Board selected KPMG to perform its 2001 SAS 70 Type I audit, and KPMG presented examples of its other SAS 70 work (NYISO MPAAS minutes, meeting of September 5, 2001: https://www.nyiso.com/documents/20142/1389491/minutes.pdf/14405e34-56be-3e04-a032-266cbe401974).
KPMG then ran NYISO's SAS 70 Type 2 audit for 11/15/2002 to 5/14/2003 (MPAAS minutes, August 26, 2003: https://www.nyiso.com/documents/20142/1403930/mpaas_082603_minutes.pdf/0980e9ee-8d8f-0ab4-3fea-6ca8ce4e7703).
FedRAMP 3PAO listed in accreditations and confirmed AICPA peer review pass (KPMG profile).
Pricing: No public price; quotes are scoped
PwC
Best for: Enterprises that want a Big Four firm with SOC, FedRAMP and HITRUST under one roof
Verified since at least 2002: ERCOT engaged PricewaterhouseCoopers to perform a Type I SAS 70 audit as of October 31, 2002 (ERCOT board memo, February 11, 2003: https://www.ercot.com/files/docs/2003/02/14/board02182003_4.doc).
PwC issued the California ISO's SAS 70 Type II report for the period starting November 1, 2005 on December 14, 2006 (CAISO presentation: https://www.caiso.com/Documents/2006PwCSAS70Presentation.pdf).
Multi-accredited (AICPA, FedRAMP 3PAO, HITRUST CSF Assessor, ISO 27001 Body) with confirmed AICPA peer review pass (PwC profile).
Pricing: No public price; quotes are scoped
Grant Thornton
Best for: Mid-market and enterprise buyers that want a national firm below Big Four scale
Verified since at least 2005: RealPage announced on April 6, 2005 that its SAS 70 Type II report was performed by Grant Thornton (https://www.realpage.com/news/realpage-completes-sas-70-type-ii-audit/).
Grant Thornton also performed RealPage's 2005 SAS 70 Type II (release of January 13, 2006: https://www.realpage.com/news/realpage-completes-2005-sas-70-type-ii-audit/).
Best for: Middle-market companies that want a national firm with a long SOC record
Verified since at least 2008: as McGladrey & Pullen, it issued InteleNet Communications' SAS 70 Type II report, announced February 12, 2008 (GlobeNewswire: https://rss.globenewswire.com/news-release/2008/02/12/1160424/0/en/InteleNet-Communications-Finalizes-SAS-70-Type-II-Certification-Process-for-Third-Year-Running.html).
Provided Businessolver's SAS 70 Type II opinion in April 2011 (release of May 18, 2011: https://www.pr.com/press-release/324724).
McGladrey LLP became RSM US LLP on October 26, 2015 (PR Newswire: https://prnewswire.com/news-releases/mcgladrey-changes-its-name-to-rsm-in-global-branding-initiative-300165670.html). Confirmed AICPA peer review pass (RSM US profile).
Pricing: No public price; quotes are scoped
Deloitte
Best for: Pre-IPO companies and multinationals that need a Big Four name on the report
Verified since at least 2008: Deloitte & Touche LLP performed i/o Data Centers' SAS 70 audit, reported August 27, 2008 (Data Center Knowledge: https://www.datacenterknowledge.com/business/i-o-data-centers-completes-sas-70-audit).
This is the earliest dated record we could fetch; Deloitte's SAS 70 practice very likely predates it, but we rank only on evidence we could check.
Best for: Buyers who want a specialist boutique with SOC, FedRAMP and HITRUST in-house
Founded in Denver in 2008; the firm says it has performed SOC 1, SOC 2 and other independent audits since 2008 (https://linfordco.com/about/).
Independent dated evidence since at least 2010: PeakColo's SAS 70 Type II audit was completed by Linford & Company, announced October 14, 2010 (https://www.newswire.com/news/peakcolo-completes-sas-70-type-ii-audit-158323).
Its own timeline lists A2LA accreditation and recognition as a FedRAMP 3PAO in 2017, and HITRUST authorization in 2017 (https://linfordco.com/about/).
Pricing: No public price; quotes are scoped
Also considered
We also checked the other directory firms with founding dates before 2011. BDO USA and Moss Adams (now part of Baker Tilly) offer SOC reporting today, but we could not fetch a dated public record naming either as a SAS 70 or SOC service auditor before 2011, so they are not ranked here. KirkpatrickPrice (founded 2005) says it has 20 years of experience (https://kirkpatrickprice.com/about/), but we found no dated SAS 70 engagement before 2011. Sensiba (founded 1977) and Dansa D'Arata Soucia (founded 1999) are long-established CPA firms, but we found no start date for their SOC practices. BARR Advisory, Johanson Group, Risk3sixty, Prescient Assurance and Insight Assurance were founded in 2014 or later per our profiles, so they cannot yet have 15 years of SOC reporting. If you have a dated source for any of these firms, send a correction and we will review it.