Framework Comparison
ISO 27001 vs SOC 2: Audit Cost, Timeline, and Which One You Need
Both are credible security frameworks. The choice depends on your market, customer base, and budget. ISO 27001 is stronger internationally; SOC 2 dominates in the US. Control overlap is 40-85%, making combined audits cost-effective.
Side-by-Side Comparison
| Dimension | ISO 27001 | SOC 2 |
|---|---|---|
| Standard owner | ISO (International Organization for Standardization) | AICPA (American Institute of CPAs) |
| Assessment type | Certification (pass/fail, certificate issued) | Attestation (auditor opinion in a report) |
| Geographic recognition | Global (strongest in EU, UK, APAC, government) | Primarily US and Canada (growing globally) |
| Initial audit cost | $20,000 - $100,000+ (Stage 1 + Stage 2 + prep) | Type I: $10,000 - $30,000 / Type II: $30,000 - $60,000 |
| Ongoing annual cost | Surveillance: $2,000 - $40,000/year | Annual Type II: $30,000 - $60,000/year |
| 3-year TCO | $24,000 - $180,000 (cert + 2 surveillance) | $90,000 - $180,000 (3 annual Type II reports) |
| Validity period | 3 years (with annual surveillance) | 12 months (annual report required) |
| Result | Public certificate (listed on CB register) | Private report (shared under NDA typically) |
| Controls framework | 93 controls in 4 categories (Annex A) | 5 Trust Service Criteria (flexible scope) |
| Audit duration | 4-20+ auditor days (by IAF mandate) | Type II: 6-12 month observation + 2-5 day audit |
When to Choose Each Framework
Choose ISO 27001 when:
- Selling to European, UK, or APAC enterprise customers
- Government contracts (many require ISO 27001 specifically)
- Global market where ISO recognition is stronger
- Industries with ISO culture (manufacturing, finance, healthcare)
- You want a public certificate (listed on CB register)
- Budget favours lower ongoing costs (cheaper surveillance vs annual SOC 2)
Choose SOC 2 when:
- Selling to US enterprise customers (standard requirement)
- SaaS/technology sector where SOC 2 is the default ask
- Customers specifically request "SOC 2 Type II report"
- You want flexible scope (choose which Trust Service Criteria to include)
- No need for formal certification (attestation report is sufficient)
- Faster initial path (Type I can be achieved in 3-6 months)
When to Get Both
Companies selling globally to enterprise customers increasingly need both frameworks. The control overlap between ISO 27001 Annex A and SOC 2 Trust Service Criteria is approximately 40-85% depending on your scope. This makes combined audits highly cost-effective.
A combined ISO 27001 + SOC 2 audit typically costs 30-40% less than two separate audits. Firms like Schellman, A-LIGN, and the Big Four (Deloitte, PwC, EY, KPMG) offer combined engagements where one audit team assesses both frameworks simultaneously.
40 - 85%
Control overlap between ISO 27001 and SOC 2
30 - 40%
Cost saving from combined audit vs separate
$45k - $120k
Typical combined Year 1 cost (medium company)
3-Year Total Cost of Ownership
The cost dynamic shifts over time. ISO 27001 has a higher Year 1 cost but lower ongoing costs (surveillance audits at $2k-$40k/year). SOC 2 has a moderate Year 1 cost but the same cost repeats annually (full Type II audit every year).
| Period | ISO 27001 | SOC 2 Type II |
|---|---|---|
| Year 1 (initial) | $30,000 - $100,000 | $30,000 - $60,000 |
| Year 2 | $6,000 - $25,000 (surveillance) | $30,000 - $60,000 (annual) |
| Year 3 | $6,000 - $25,000 (surveillance) | $30,000 - $60,000 (annual) |
| 3-Year Total | $42,000 - $150,000 | $90,000 - $180,000 |
Ranges are for medium-sized organisations (51-250 employees) using mid-tier audit firms. Excludes preparation costs.
Frequently Asked Questions
Is ISO 27001 harder than SOC 2?
ISO 27001 is generally considered more prescriptive and comprehensive. It requires a formal ISMS with documented risk assessment, Statement of Applicability, and 93 specific controls. SOC 2 is more flexible, allowing organisations to define their own controls against the Trust Service Criteria. However, SOC 2 Type II requires a longer observation period (6-12 months of evidence). Both are achievable for well-prepared organisations.
Is ISO 27001 more expensive than SOC 2?
In Year 1, ISO 27001 is typically more expensive ($20k-$100k+ vs $30k-$60k for SOC 2 Type II). However, over a 3-year period, the costs converge because SOC 2 requires an expensive annual audit while ISO 27001 has cheaper surveillance audits in Years 2 and 3. 3-year TCO for both is roughly $90k-$180k for mid-sized companies.
Can one auditor do both ISO 27001 and SOC 2?
Some firms offer combined ISO 27001 + SOC 2 audits (notably Schellman, A-LIGN, and the Big Four). This can save 30-40% compared to separate audits because of the 40-85% control overlap. The same auditor team assesses both simultaneously, reducing duplicate evidence collection and interview time.
Which should a startup get first?
For US-focused SaaS startups: SOC 2 Type II first (most US enterprise customers expect it). For companies selling internationally or to EU/UK customers: ISO 27001 first. For companies selling to both markets: consider a combined audit from the start, as adding the second framework later costs nearly as much as doing it alone.