Financial Due Diligence Guide for SaaS Founders

What due diligence actually is

Due diligence is the process by which investors verify that what you told them during the pitch is actually true. It is not a formality. It is the point where investors go from "we are interested" to either "we are investing" or "we are walking away."

For most founders, due diligence feels adversarial. Someone is going through your finances with a magnifying glass, asking questions you do not know the answers to, and requesting documents you have never thought about.

It does not have to be this way. If you prepare properly, due diligence becomes a straightforward exercise in organised information sharing. If you do not prepare, it becomes the thing that kills your deal.

What investors look for

1. Revenue quality

This is the single most scrutinised area. Investors want to understand not just how much revenue you have, but the quality and durability of that revenue.

Recurring vs non-recurring: What percentage of revenue is genuinely recurring (subscriptions) versus one-off (professional services, setup fees, consulting)? A business with £1M ARR at 90% recurring is worth materially more than one with £1M revenue at 50% recurring.

Customer concentration: What percentage of revenue comes from your top 5 customers? If one customer represents 40% of ARR, that is a significant risk. Investors typically get uncomfortable above 20% concentration in any single customer.

Cohort analysis: How do customer cohorts behave over time? Do customers from 2023 spend more or less today than when they signed up? Expansion within cohorts is a strong positive signal. Decay is a red flag.

MRR movements: They want to see the monthly waterfall — new logos, expansion, contraction, and churn — for at least the last 12 months. Ideally 24. The trend matters more than any single month.

2. Unit economics

LTV:CAC ratio: Is the business acquiring customers profitably? A ratio below 3:1 raises questions about the sustainability of the growth model.

CAC payback period: How long does it take to recover the cost of acquiring a customer? If payback exceeds 18 months for an SMB-focused product, investors will question whether the economics work.

Gross margin: SaaS businesses should have gross margins of 70-85%. If yours is below 60%, they will ask why. Hosting costs, support costs, and professional services can all drag margins down.

3. Cash flow and burn

Monthly burn rate: How much cash are you consuming each month after all revenue is collected? What is the trend?

Runway: How many months of cash do you have at current burn? This tells investors how urgent the raise is — and how much negotiating leverage you have.

Cash conversion: How efficiently do you turn bookings into cash? Annual upfront billing converts immediately. Monthly billing with net-30 terms creates a lag. Enterprise deals with net-60 terms create a bigger lag.

4. Financial controls and accuracy

Revenue recognition: Are you recognising revenue correctly? Recognising a 12-month annual contract as £12,000 in month one (instead of £1,000/month) is a material misstatement that will be caught.

Accruals and prepayments: Are costs matched to the correct periods? Paying annual insurance of £12,000 should not appear as a £12,000 expense in January — it should be spread across 12 months.

Bank reconciliation: Does your accounting system match your bank statements? Any unexplained differences are a red flag.

5. Tax compliance

Corporation tax: Are your returns up to date? Any outstanding liabilities?

VAT: Are you registered (you should be if turnover exceeds the £90,000 threshold)? Are returns filed on time? Any outstanding payments?

PAYE/NIC: Are payroll taxes being deducted and paid correctly? HMRC penalties for late payment are severe.

R&D tax credits: Have you claimed them? If not, why not? If you have, are the claims defensible?

Building your data room

A data room is a secure online folder structure containing all the documents investors need. Start building it before you start fundraising — not when investors ask for it.

Folder structure

Corporate:

• Certificate of incorporation
• Articles of association (current version)
• Shareholders agreement
• Share cap table (fully diluted, including option pool)
• Board minutes for the last 12 months
• Any existing convertible notes, SAFEs, or loan agreements

Financial:

• Monthly management accounts for the last 24 months
• Annual statutory accounts (filed at Companies House)
• Current year budget vs actuals
• Financial model with forecasts (3-year minimum)
• Bank statements for the last 6 months
• Accounts receivable and payable ageing reports

Revenue:

• MRR schedule showing customer-level monthly revenue
• Cohort retention analysis
• Customer contract templates (standard terms)
• Top 10 customer contracts
• Churn analysis with reasons

Tax:

• Corporation tax returns and computations (last 2 years)
• VAT returns (last 4 quarters)
• R&D tax credit claims and supporting documentation
• Any HMRC correspondence or investigations

Legal:

• Material contracts (partnerships, resellers, OEMs)
• IP assignments (ensure all founder and employee IP is assigned to the company)
• Data protection registration and GDPR compliance documentation
• Terms of service and privacy policy
• Any outstanding or threatened litigation

People:

• Organisation chart
• Employee list with start dates, titles, and compensation
• EMI option scheme documentation
• Key person dependencies

Common red flags that kill deals

Red flag 1: Numbers that do not reconcile

If your pitch deck says £800,000 ARR but your management accounts show £650,000 of recognised revenue, investors will ask why. The answer is usually sloppy MRR tracking or confusion between booked and recognised revenue. Neither is acceptable.

Red flag 2: Missing or late filings

Outstanding Companies House filings or overdue HMRC returns signal disorganisation. They are also easy to fix before fundraising starts. There is no excuse for having them outstanding when you enter due diligence.

Red flag 3: Customer concentration

One customer at 40% of revenue is a single point of failure. If that customer churns, you lose nearly half your business. Investors will price this risk heavily, if they proceed at all.

Red flag 4: No separation between personal and business finances

This is more common at pre-seed and seed than Series A, but if the founder's personal expenses are running through the company accounts, it creates a compliance mess and signals poor financial discipline.

Red flag 5: Inconsistent metrics

If your investor deck shows one set of numbers, your management accounts show another, and your CRM shows a third, trust evaporates. One source of truth for every metric.

Red flag 6: Unexplained revenue spikes or drops

Any unusual movement in revenue needs a clear explanation. A one-off enterprise deal, a pricing change, a refund — investors will ask. If you cannot explain it, they will assume the worst.

Red flag 7: IP not properly assigned

If your CTO wrote code before joining the company, is that IP assigned to the company? If contractors built features, are the assignments documented? Unclear IP ownership can block a deal entirely.

The timeline

Expect due diligence to take 4-8 weeks for a Seed or Series A round. More complex deals (Series B+, PE-backed) can take 12 weeks or more.

Weeks 1-2: Data room access, initial document review, follow-up questions list.

Weeks 3-4: Deep dives into specific areas (revenue quality, financial model assumptions, legal review). Commercial due diligence may happen in parallel (customer reference calls, market analysis).

Weeks 5-6: Follow-up questions, clarification calls, additional document requests.

Weeks 7-8: Final report, negotiation of any findings, deal documentation.

How to prepare

Start 3-6 months before you plan to raise:

1. Clean your books. Ensure management accounts are accurate, accruals are correct, and revenue recognition is properly applied.

2. Build your data room. Do not wait for the first investor request. Have everything organised and ready.

3. Reconcile your metrics. MRR in your CRM must match MRR in your accounting system must match MRR on your investor deck. One source of truth.

4. File everything. Companies House annual return, confirmation statement, statutory accounts. HMRC: corporation tax, VAT, PAYE. All current and up to date.

5. Fix known issues. IP assignments, outstanding contracts, employee documentation. Every issue you know about should be fixed before investors discover it.

6. Prepare a Q&A document. Anticipate the questions investors will ask and prepare clear, honest answers. Business anomalies (a big churn month, a one-off revenue spike) should be explained proactively.

The best outcome is an investor who says, "This was the most organised data room we have seen." It sets the tone for the entire relationship and signals that you run a disciplined business.