Technical Due Diligence: What Really Gets Checked Before You Invest In (or Buy) a Startup

Technical due diligence is the independent assessment of a company's software, team, and technical risks, done before investing or acquiring, to understand whether behind the sales narrative there's a solid asset or hidden debt. In a round or an acquisition, the pitch tells the vision; technical due diligence checks whether the product that backs it actually exists, holds the load, and is yours after closing. It's the difference between buying an engine and buying a photo of the engine.

What it is (and why it's not just any audit)

The technique is the same as a code audit, but the context and the stakes change. A technical audit is commissioned by the owner to understand and improve their own software. Due diligence is commissioned by whoever is about to put money in: an investor or an acquirer who has to assess someone else's asset before a transaction. The output changes: not an internal roadmap, but a judgment useful to decide whether to close the deal, at what price, and on what terms.

What a technical due diligence checks

You don't read every line of code: you look for the risks that move the value. In practice, five areas.

Code and architecture

Quality, order, and readability of the code, presence of tests, architectural choices consistent with what the product will need to become. Perfection isn't required: what you need is to understand how much it will cost to maintain and grow, and how much technical debt comes along with it.

Team and bus factor

Who wrote the software, and what happens if that person leaves. If a single person knows how everything works — the dreaded bus factor of one — you're buying a risk, not just a product. You also look at how much the team depends on irreplaceable external consultants.

Security and compliance

Handling of personal data (and GDPR compliance), secrets and passwords in the repository, known vulnerabilities in dependencies, access control. A hole here isn't a technical detail: it's a potential liability you inherit at closing.

Intellectual property and licenses

The question that's worth the deal: does the code really belong to the company?Contracts with employees and freelancers that assign ownership, open source licenses compatible with commercial use, no component that forces you to make your code public. If the IP isn't clean, you're buying far less than you think.

Infrastructure, scalability, and cost

How it runs in production, what it costs today, and what it will cost at 10x the users. An architecture that holds 1,000 users but blows up at 50,000 changes the plan — and the price. Here you take apart the almost-always-optimistic assumption that it "scales without problems".

The red flags that break (or reprice) a deal

Some problems get fixed after closing. Others change the valuation or make you walk away from the table. These are the ones I weight:

• Bus factor of one. A single person knows the entire system, with no documentation and no redundancy.
• Unclear intellectual property. Code written by freelancers with no signed assignment, or licenses incompatible with commercial use.
• Zero tests and no separate environment. Every change is a gamble in production: future maintenance cost is high and unpredictable.
• Secrets in plain text and neglected security. Keys and passwords in the repository, sensitive data unprotected: liabilities waiting to surface.
• Metrics that don't hold up to the raw data. When the pitch numbers don't add up once you look at the source, the problem is no longer just technical.

How it's run, in practice

It's not a surprise inspection: it's a collaborative, confidential process, usually a few days for an early-stage startup and one to two weeks for a mature product. Broadly:

• Read-only access to the repository, documentation, and environments, under NDA.
• Analysis of the code and architecture, with automated tools and targeted reading of the parts that matter.
• Interviews with the technical team, where the risks the code alone doesn't reveal often surface.
• A written report with a clear judgment, risks ranked by severity, and the impact on the deal — readable even by non-technical people.

Who commissions it and when

Usually whoever puts up the money: business angels, venture capital or private equity funds, or a company acquiring another. But increasingly the selling foundercommissions it too, to arrive at the table with a clear picture already in hand and negotiate from a position of strength instead of enduring the other side's discoveries. The right moment is before the final term sheet: due diligence exists to confirm or correct its terms, not to decorate a deal that's already closed.

In short

Technical due diligence turns "it looks like a good product" into an informed decision. It tells you whether you're buying an asset or a liability, where the risks are, and what they're worth in terms of price and terms. On a six- or seven-figure deal, it's the spend with the best return.

Frequently asked questions

Weighing an investment or an acquisition and need someone to look under the hood before you sign? I run independent technical assessments, and if after closing you need a technical lead to grow the product I also work as a Fractional CTO. First call free, reply within 24 hours.