What does technical due diligence actually look at?

Four things, in roughly this order of how often they cause trouble: whether the company actually owns its intellectual property, whether the codebase can survive the departure of one person, whether the architecture can carry the next eighteen months of plan, and whether the security and data handling would survive a customer asking about it.

What is the most common finding?

Broken chain of title on the code. Under the Copyright, Designs and Patents Act 1988 the author owns copyright unless it is assigned in writing, and the employee exception does not reach contractors — so any freelancer who worked on the product without a signed assignment still owns their part of it. It is extremely common and it is fixed retrospectively, which means tracking people down.

Due diligence

What does technical due diligence cost?

Q: What does technical due diligence cost?

Price it from days. A pre-seed codebase is typically three to five days of senior engineering time; a Series A company with infrastructure and a team is eight to fifteen. At the UK median contract rate of £525 a day that is roughly £1,600 to £2,600 at the small end and £4,200 to £7,900 at the larger one.

Last updated 7 October 2026

Search for this and you get a dozen checklists, none of them with a price and most of them the same checklist. The checklist is the easy part. What it costs, and what it is actually looking for, is the part worth writing down.

What it costs, from days

UK contract software developer, median day rate

£525

Six months to 6 October 2026, 257 quoted rates across 441 adverts. Source: ITJobsWatch. Senior review work bills above the median, so treat the figures below as a floor rather than a quote.

What is being reviewed	Days	At £525/day
Pre-seed: one product, small codebase, no team	3–5	£1,600–2,600
Seed: live product, some users, one or two developers	5–8	£2,600–4,200
Series A: infrastructure, a team, real customers	8–15	£4,200–7,900
Acquisition: everything above plus IP and licence tracing	12–25	£6,300–13,100

Anyone quoting a flat band without asking how big the thing is has not scoped it. Ask for the day count; if they cannot give one, they have not thought about your company.

The investor and the acquirer want different things

This gets conflated constantly, and the two reviews genuinely look in different places.

	Investor	Acquirer
Core question	Can they build the next 18 months?	Can we own and run this?
Weighs most	Team, velocity, architecture headroom	IP chain of title, licences, key-person risk
Tolerates	Technical debt with a plan	Very little undocumented anything
Kills the deal	No one who can carry the roadmap	Code the company does not own

The four things actually examined

Do you own it? Written assignments from every contractor who ever touched the code, plus the open-source licences embedded in the product. See the ownership page for why this is so often broken.
What happens if one person leaves? Commit concentration, whether anyone else can deploy, whether there is a written runbook. A bus factor of one is survivable in a seed company and a serious problem in an acquisition.
Will the architecture carry the plan? Not whether it is elegant. Whether the next eighteen months of roadmap can be built on it without a rewrite, and what the rewrite would cost if not.
Would the security answers survive a customer? Where personal data sits, who can reach production, whether backups have ever been restored. The same ground as an enterprise security review, which is not a coincidence.

The finding that most often causes trouble

Chain of title. Under section 11(1) of the Copyright, Designs and Patents Act 1988 the author of a work is its first owner, and the employee exception in section 11(2) does not reach a contractor. Section 90(3) says an assignment is ineffective unless in writing and signed. So every freelancer who ever worked on your product without a signed assignment still owns their contribution.

This is extremely common, it is almost never deliberate, and it is fixed retrospectively — which means contacting people you parted with years ago and asking them to sign something. Some want paying. Some do not reply. It is much cheaper to find this out before an investor does.

The version worth buying before anyone asks

The useful time to run this is not when an investor demands it. It is three months earlier, on your own terms, with the report written for you rather than for them. Then the findings are a to-do list instead of a negotiating position, and the assignments get signed while everyone is still friendly.

Two to three days, a written report, and a prioritised list of what to fix before anyone external looks. It is the cheapest insurance available on a round.

Sources. Day rate: ITJobsWatch, UK contract software developer, median £525/day, six months to 6 October 2026, retrieved 7 October 2026. Copyright: CDPA 1988 s.11 and s.90. The day ranges and the investor-versus-acquirer table are my own, from doing this work. Nothing here is legal advice.

Got a term sheet and a codebase?

Tell me the stage and roughly the size of the thing. You get a scope, a fixed price and a date — and the report is yours, not the investor’s.

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