Technical Due Diligence & System Audits

Technical Due Diligence (TDD) is the independent evaluation of a company's technology before a significant financial event — a Series A or Series B investment, a private equity acquisition, a merger, or a pre-exit health check. It's the technical equivalent of a financial audit, and for deals above £1M in the UK tech market it has become effectively non-negotiable.

What Gets Missed Without a Technical Due Diligence

I've seen deals close where the acquirer later discovered the entire product ran on a single developer's laptop cron jobs. I've reviewed codebases with zero automated tests that were presented as "enterprise-grade." I've found AWS bills that would triple at 2x the current user base because nobody had reviewed the architecture. These aren't edge cases — they're common, and they're expensive.

A proper TDD surfaces four classes of risk before money changes hands: code quality debt that will slow the next 12 months of delivery, security and GDPR exposure you're about to inherit, scalability ceilings that invalidate the growth case, and team dependencies that can vanish overnight if a single senior engineer leaves.

My Approach to Technical Due Diligence

I bring 18+ years of system architecture experience to every audit. I don't use automated scoring tools and call it a day — I read the code, interview the team, stress-test the infrastructure, and map the data flows. The result is a report that tells you exactly what you're buying, what it will cost to fix, and whether the team can execute on the roadmap.

Based in Manchester, I work with UK-based VC firms, PE funds, and founders across the country. In-person debriefs are available for London and Manchester — remote for everywhere else.

A Typical Technical Due Diligence Checklist

Every engagement is tailored to the deal, but the checklist I work through looks roughly like this:

• Code quality — static analysis, test coverage, cyclomatic complexity, code-smell hotspots
• Architecture — service boundaries, data flow diagrams, coupling and cohesion, obvious scalability ceilings
• Security — OWASP Top 10 review, secrets management, authentication and session design, GDPR data-flow mapping
• Infrastructure — cloud cost projections at 2x and 10x scale, backup and disaster-recovery posture, monitoring and alerting maturity
• Third-party risk — dependency freshness, critical CVE exposure, open-source license compatibility
• Team — bus factor, seniority distribution, CI/CD maturity, code-review and incident-response practices
• Compliance — GDPR, ISO 27001 readiness, and UK-specific regulatory alignment where relevant

How Much Does Technical Due Diligence Cost in the UK?

Pricing depends on system size, stack diversity, and the number of repositories involved. As a rough guide: a lightweight pre-investment screening sits around £2,500, a standard Series A TDD ranges £7,500–£10,000, and a full acquisition-grade audit covering multiple services and a sizeable engineering team runs £10,000–£15,000. All engagements are fixed-price after a free scoping call, so you know the total cost before committing.

In deal terms that is typically less than 0.5% of the transaction size. In most of the engagements I've run, the findings translated directly into negotiation leverage on price or remediation budget that paid the audit back many times over.

Who Commissions a Technical Due Diligence

Venture capital firms evaluating Series A or Series B investments, often in parallel with commercial and financial diligence. Private equity funds conducting pre-acquisition audits or portfolio technical reviews. Founders preparing their company for a fundraise or exit, wanting to fix the obvious red flags before investors find them. Boards mandating an independent technical review after a CTO transition or a significant incident. If any of these describe your situation and you're in the UK, let's discuss the scope and timeline for your audit.