Technical due diligence is the review an investor, acquirer, or their hired technical team runs on your codebase before a fundraise, acquisition, or IPO closes. Someone with real engineering judgment, not a form or a checklist, reads your code, talks to your engineers, and decides whether what you've built matches the story in your pitch deck.
Most guides to technical due diligence assume every line in your repo was written by someone who still works for you. That's rarely true for an early-stage company. A chunk of your product, sometimes most of it, was probably built by a contractor, a freelancer, or an outsourcing agency before you made your first full-time engineering hire, and that's exactly where diligence tends to turn up surprises.
What is technical due diligence, and when does it happen?
Three events trigger it, per Snyk's overview of technical due diligence: a fundraise, where investors want assurance before they wire money; an acquisition, where the buyer wants to know what they're actually inheriting; and an IPO, where public-market scrutiny raises the bar on everything. The review can run alongside financial and legal due diligence or as its own track with its own timeline.
Who runs it varies. Larger investors and acquirers often have their own technical team run the review. Whoever runs it, you're not choosing the reviewer. You're choosing how ready you are when they show up.
What a technical due diligence review actually checks
The checklists vary in length and order, but lined up together, Snyk's overview, M&A Science's technical due diligence checklist, and others converge on the same six areas:
| Area | What reviewers look for |
|---|---|
| Architecture and scalability | Whether the system design holds up under far more load than it sees today, and where the bottlenecks are |
| Security | Authentication, data handling, dependency vulnerabilities, and incident history |
| Code quality and test coverage | How much of the codebase has automated tests, and how consistent the code is across contributors |
| IP and licensing | Who legally owns the code, and whether any open-source dependencies carry terms that restrict resale |
| Team and process | Who wrote what, how decisions get made, and what happens if a key person leaves |
| Documentation | Whether architecture decisions and system knowledge live anywhere a new engineer could find them |
Each of these gets harder to answer cleanly once part of your codebase was built outside your own team.
What diligence asks about outsourced, nearshore, or contractor-built code
The published due diligence guides read for this piece skip this part entirely. Many early-stage products are built, at least partly, by contractors, freelancers, or an agency before the company makes its first full-time engineering hire. Diligence flags exactly that pattern, and the questions get specific fast.
Who owns the code your contractors wrote?
Ownership doesn't transfer automatically just because you paid the invoice. Depending on the contract and the jurisdiction, a contractor or agency can retain rights to code they wrote for you unless the agreement explicitly assigns intellectual property to your company. Staff augmentation works differently: the engineer works inside your codebase, under your direction, as part of your team, so the ownership line between the two models is a lot clearer from the start.
Check your own contracts before a reviewer asks you to prove you own your product, not after. This is the general shape of the issue, not legal advice for your specific agreement or jurisdiction.
What your contractor and vendor agreements need to say
An assignment-of-IP clause is the baseline: language that explicitly transfers ownership of the work product to your company, not just a license to use it. Without one, you might have the right to use the code but not the right to sell it, relicense it, or show a reviewer a clean chain of title.
If the contractor or vendor touched customer data anywhere along the way, you need a data processing agreement too. What a data processing agreement has to cover walks through the minimum terms: the subject matter and duration of the processing, the categories of data involved, the processor's obligations, and what happens to the data when the contract ends. A contractor agreement that's silent on IP assignment and silent on data processing is two separate problems, not one.
Bus factor: what happens if your outsourced team leaves before the deal closes
Bus factor is the number of people who could disappear before a project stalls out. For an outsourced team, that number is often uncomfortably low: one contractor, or one small team at an agency, who wrote the parts of your system nobody else has touched since.
A reviewer can't interview someone who's no longer under contract. If the agency that built your payment integration wrapped up the engagement eight months ago and nobody on your current team has touched that code since, a diligence reviewer has to take your word for how it works, and that's not a position you want to put them in. Staff and IP retention through a handover is a risk area most vendor pages mention least, if at all, including in build-operate-transfer engagements, where it's flagged as something to plan for rather than something the contract resolves on its own. Most straightforward contractor agreements don't raise it at all.
The documentation gap outsourced teams leave behind
Architecture decisions made by a contractor or an agency rarely end up in the repo. They end up in a Slack thread, an email, or the head of someone who isn't on the account anymore. When the engagement ends, that context usually doesn't get handed over in writing, because nobody's contract required it to.
A diligence reviewer who reads the actual code, not just a summary someone wrote about it, applies the same logic behind engineer-led vetting: judge the real work, not a proxy for it. They'll notice the gap fast: commit history with no comments, a README that stops updating the day the contractor's invoice does, decisions with no record of why they were made. The fix starts before you're in a diligence process, not during one.
How to prepare for technical due diligence before a fundraise or acquisition
Many startups without a full-time CTO bring in a fractional one specifically to run this list. A fractional CTO's role in due diligence prep usually includes building the architecture narrative and assembling the documentation a reviewer will ask for, on top of whatever else they're doing for you day to day. If you're doing it yourself, work through it in this order.
1. Inventory your IP and contractor agreements
Pull every contractor, freelancer, and agency agreement you've signed since day one. For each one, confirm there's an assignment-of-IP clause, and flag any that are missing one or use vague language like "work product" without saying who owns it. This is a common gap in an early-stage codebase, and it's cheaper to fix months ahead of a deal than during one.
2. Document architecture decisions
Explain why the system is built the way it is: why you chose the database you chose, why a service is split the way it's split, what tradeoffs got made under time pressure. This is the context a reviewer can't get from reading code alone, and it's usually the first thing missing when the person who made the decision is a contractor who left a year ago.
3. Review your own code and dependencies before someone else does
Some vendors sell this step as a stand-alone code audit. Either way, look for outdated dependencies, unlicensed or copyleft open-source packages that could complicate resale, and code with no test coverage in the parts of the product that matter most. Finding a problem yourself, with a plan already in hand, reads very differently to a reviewer than having them find it first.
4. Close open security gaps
Fix what you found in step three, starting with anything touching authentication, payments, or customer data. A reviewer who finds an open vulnerability you already knew about and hadn't fixed will ask why, and there's no good answer to that question.
5. Know your bus-factor risk points
List every system where only one person, employee or former contractor, understands how it actually works. You don't need to eliminate every one of these before a deal, but you need to know where they are and have a plan, cross-training, better documentation, a retainer with the original contractor, before a reviewer finds one you didn't know about.
FAQ
How long does technical due diligence take?
It depends on who's asking. mev.com's technical due diligence guide puts the typical timeline at two to four weeks. TechCXO's due diligence page puts it at two to three weeks. Either way, the timeline usually bends around how fast you can produce documentation that doesn't exist yet, more than around the reviewer's own schedule.
What happens if technical due diligence finds a problem?
It depends on the size of the problem. A missing IP assignment clause or an undocumented bus-factor risk usually shows up as a condition: fix it before close, or accept a price adjustment that reflects the risk. A genuinely broken architecture or an unresolved security breach can kill the deal outright. Most findings land somewhere in between, a list of items the buyer or investor wants addressed on a timeline, sometimes before close and sometimes as a post-close condition.
Who pays for technical due diligence, the buyer or the startup?
The party running the review usually pays for it, whether that's their own technical team's time or a firm they've hired. Where it gets less clean is the startup's side of the cost: pulling contracts, writing documentation that didn't exist before, and pausing engineering work to answer questions all come out of your team's time, and none of that shows up on anyone's invoice.