SOC 2 audit firm fees: Big 4, mid-tier, and boutique CPA pricing.
Three audit-firm tiers
| Firm tier | Type 1 fee | Type 2 fee | When justified |
|---|---|---|---|
| Big 4 (Deloitte, EY, KPMG, PwC) | £60,000+ | £100,000+ | Downstream buyer requires Big 4 signatory: banks, defence, certain regulated insurers. Multi-entity global programmes. |
| Mid-tier / regional | £18,000 – £35,000 | £25,000 – £60,000 | Most series-B+ SaaS. Mature engagement processes, strong technical depth, fee transparency. |
| Boutique CPA (SOC-2-specialist) | £12,000 – £18,000 | £18,000 – £35,000 | First-time SOC 2 at startup or seed-extension stage. Specialised in SaaS attestation, lean engagement teams. |
Big 4 firms do strong work. The premium is real, and pays back in two cases: where a downstream buyer requires the Big 4 signatory by name, and where the engagement itself benefits from Big 4 process discipline (multi-entity, multi-region, highly regulated). Outside those cases, mid-tier and boutique CPAs deliver the same SOC 2 attestation under the same AICPA standards.
What drives an audit fee
SOC 2 audit fees are partner-manager-senior-staff hours multiplied by the firm's rate matrix. For a typical mid-tier CPA on a Type 2 audit of a 25 to 50 employee SaaS, the breakdown lands roughly at 30 to 50 partner hours, 80 to 120 manager hours, 120 to 200 senior hours, and 100 to 200 staff hours. Rates are firm-confidential but cluster around £400 partner, £250 manager, £180 senior, £120 staff for mid-tier UK and US firms.
Two factors move the hour count materially. The first is Trust Services Criteria scope, which adds roughly 18 percent per added optional criterion. The second is environment complexity: number of cloud regions, number of microservices in scope, number of vendors with material data access. Each additional vendor with data access typically adds 4 to 8 staff hours of vendor-management testing.
Hidden line items
| Line item | Typical surcharge | Notes |
|---|---|---|
| Out-of-scope work (extra entity) | +15 to 25% | Each additional entity (subsidiary, acquired company) brings its own walkthroughs, sample tests, control owner interviews. |
| Re-issuance of report | £3,000 – £8,000 | Customer requests a corrected or re-dated report. Cost depends on whether re-fieldwork is required. |
| Expedited timeline | +15 to 30% | Compressing the engagement into 60 percent of standard duration, typically by adding a second senior to the team. |
| Observation period extension | £4,000 – £12,000 | Extending the Type 2 window from 6 to 12 months mid-engagement. Includes re-sampling. |
| Carve-out / inclusive method changes | +5 to 10% | Switching how subservice organisations are described in the report mid-engagement adds documentation and management response work. |
When to choose which tier
The right tier is rarely the cheapest. It is the tier whose engagement style fits how your team will run readiness and evidence collection. A boutique CPA expects you to ship evidence on schedule. A Big 4 firm expects you to manage the project around their methodology. A mid-tier sits between and usually offers the cleanest fit for a series-A to series-C SaaS.
For first-time SOC 2 at startup stage, boutique CPA is the usual right choice unless a customer requires otherwise. For scale-ups with concurrent ISO 27001 or HIPAA programmes, a mid-tier firm with multi-framework practice usually beats the same firm running each framework in isolation.
What a fair quote looks like
For a 35-person SaaS, Type 2, Security and Confidentiality in scope, single AWS environment, single CRM and HR vendor, a fair mid-tier CPA quote in 2026 lands around £32,000 for the audit engagement. The SOW lines should be visible.
| SOW line | Typical hours / fee | What you should expect |
|---|---|---|
| Planning and scoping | 12 to 20 hours · £3,500 | Agreed scope memo, control list, sample population definition, vendor list. |
| Walkthroughs and design assessment | 30 to 50 hours · £8,000 | Interview each control owner, document operating procedure, identify design gaps before fieldwork. |
| Sample testing and fieldwork | 60 to 100 hours · £14,500 | Sampled testing across the observation window, evidence review, exception logging. |
| Reporting and management response | 20 to 30 hours · £6,000 | Draft report, exceptions discussion, management response, final attested report. |
Bundled engagements
Where the same audit firm is also engaged for adjacent attestation or compliance work, combined-engagement discounts are typical. Concurrent SOC 2 plus ISO 27001 audits with a dual-accredited firm typically save 10 to 20 percent compared with separate engagements. The same firm running SOC 1 and SOC 2 typically discounts the second by 15 to 25 percent. If the same audit firm is also engaged for PCI DSS, the combined-engagement discount is typically 10 to 15 percent on each. The PCI side of that math is at pcicompliancecost.com.
Cross-reference
Firm tier interacts with the GRC platform decision; the GRC platforms page sets out where platform fee replaces audit hours. Trust Services Criteria scope drives roughly 18 percent of audit fee per added optional criterion; the math is on the Trust Services Criteria page. For year 2 onward, audit fees behave differently to year 1; see the ongoing cost page. For the 100 to 500 employee bracket where mid-tier is the standard fit, see the scale-up cost page.