When you sell, the buyer’s team spends weeks testing every claim in your information memorandum. A seller who answers from a prepared, consistent file gives them fewer reasons to reopen the price or stretch the timetable.
This guide is written for the seller. It covers the documents buyers ask for, how to get the company itself ready, when to open a data room and how long diligence usually takes. For a definition of the process and its types, read what due diligence involves.
Last reviewed: October 2026.
To sell a company with fewer surprises, gather seven sets of documents (corporate and legal, financial, tax, commercial, people, IP and technology, and operations and compliance), fix the gaps a buyer will find, and load everything into a data room before the first buyer asks. Expect buyer diligence to run about 30 to 90 days after a letter of intent, and start preparing months earlier.
- Prepare the company, not only the documents: fix gaps in the seven checklist areas before a buyer finds them.
- Set up the data room at least four to six weeks before formal diligence, and do not wait for a signed letter of intent.
- Plan for about 30 to 90 days of buyer diligence and six to twelve months for the whole sale.
- Release sensitive documents in stages, and route every buyer question through one owner.
What due diligence means when you are the seller
On the sell-side, due diligence has two parts. The first is the buyer’s review of your company: they request documents, ask questions and test your numbers. You cannot control what they ask, but you can control how ready you are.
The second is optional: a vendor due diligence report, where an independent adviser reviews your financials or legal position before you go to market. In a sale, “vendor” means the seller. It lets you find and fix problems on your own schedule, and gives buyers a report to start from.
The checklist below covers both. Treat each item as a question a buyer will ask, and make sure you can answer it with a document.
Due diligence checklist for selling a company
Use this table in three passes: confirm you have each document, check that it matches your other documents, then fix the item in the last column before buyers see it.
| Area | The buyer is asking | Have ready | Fix before launch |
|---|---|---|---|
| Corporate and legal | Who owns the company, and can the sellers sign? | Certificate of incorporation, articles, cap table, shareholder agreements, board minutes, subsidiary list, litigation log | Gaps in the share register, minutes that were never signed, undocumented side agreements |
| Financial | Are the numbers real and repeatable? | Three to five years of financial statements (audited if available), monthly management accounts, current budget and forecast, debt schedule, working capital history | Management accounts that do not tie to statutory accounts, unexplained one-off items, forecasts that ignore history |
| Tax | Does any exposure come with the company? | Corporate tax returns, VAT or sales tax filings, correspondence with tax authorities, payroll tax records | Late or missing filings, open queries with tax authorities |
| Commercial | Will revenue survive the sale? | Contracts with top customers, revenue by customer and product, pipeline, churn, pricing, key supplier contracts | Change-of-control or exclusivity clauses, one customer above a large share of revenue, contracts that expired and continue informally |
| People | Will key people stay, and what do they cost? | Org chart, senior employment contracts, bonus and equity plans, contractor list | Missing signed contracts, contractors who look like employees, equity promises that were never documented |
| IP and technology | Does the company own what it sells? | Trademarks, patents, domains, software licences, open-source use, IT systems overview, security policies, incident log | IP built by contractors without an assignment, licences that end on a change of control, unpatched systems |
| Operations and compliance | Can it run without the owner and stay compliant? | Licences and permits, process documentation, insurance schedule, data protection policies, supplier list | Processes that live in one person’s head, expired permits, no insurance summary |
The last column is where value is protected. A gap you found yourself is a task. A gap a buyer finds is a negotiating point.
For a document-by-document list that applies to every deal type, see the full data room due diligence checklist.
A printable three-page version of this checklist with a tick box for every document and every fix.
What documents do I need to sell my business?
If you only have time to pull ten things together, start with these. Buyers usually ask for them in the first request list, and most of the rest follows from them:
- Financial statements for the last three to five years, plus year-to-date management accounts
- Tax returns for the same period
- Cap table and share register
- Contracts with your largest customers, and revenue by customer
- Key supplier agreements and property leases
- Senior employment contracts and incentive or equity plans
- An employee list with roles, pay and notice terms
- Proof of IP ownership: trademarks, patents, domains and software licences
- Licences, permits and insurance policies
- A log of any litigation or disputes, past and pending
Exact requirements depend on your country, industry and deal size, so confirm the final list with your M&A adviser and lawyer.
Release documents in stages. You do not need to show everything on day one. A common pattern is summary financials and anonymised customer data before the letter of intent, full documents after it, and the most sensitive items (named employee data, customer contracts with pricing) only in the confirmatory phase and only to the people who need them. Staged access is easier to manage with permissions in a data room than with email attachments.
How do I prepare my company for a sale?
Preparing the company matters more than preparing the folders. These eight steps put the work in the order it usually has to happen:
If you are also working out how to structure the room itself, follow the step-by-step guide to preparing a virtual data room.
How early should I set up a data room before selling?
Set it up at least four to six weeks before formal diligence starts, and do not wait for a signed letter of intent. Missing documents and inconsistencies take time to resolve, and that time is cheap before a buyer is watching and expensive after. A due diligence data room can stay in staging, invisible to buyers, until you decide to go live.
The four to six weeks is a floor. Items with long lead times, such as audited accounts, tax filings that are behind or IP assignments from former contractors, need longer. One broker guide suggests starting preparation 12–24 months before a planned exit for the cleanest outcome.
| When | What to do |
|---|---|
| 12–24 months before exit (ideal) | Start the clean-up: accounts, contract renewals, IP assignments, key-person arrangements |
| 3–6 months before launch (practical target) | Run your own diligence, fix gaps, draft the information memorandum, open the room in staging |
| 4–6 weeks before formal diligence (minimum) | Upload and index every document, set permissions, test the room as a buyer would |
| Letter of intent signed | Give access to the chosen buyer groups and start the Q&A process |
For the room setup itself, see the step-by-step guide to preparing a virtual data room.
How long does due diligence take when selling a company?
Buyer due diligence usually takes about 30 to 90 days after the letter of intent is signed, and the whole sale usually takes six to twelve months. Small, well-prepared deals can be faster. Complex or regulated businesses run longer.
| What is measured | Typical range | Source |
|---|---|---|
| Buyer due diligence after the letter of intent | 30–60 days | Barnes Walker |
| Buyer due diligence once buyers are engaged | 8–12 weeks | Kahn Litwin |
| Letter of intent to closing, with diligence running alongside contract negotiation | 90–120 days | McLane Middleton |
| Whole sale, from preparation to closing | 6–12 months | The Advisory |
The ranges differ because they measure different things and different deal sizes, so treat them as planning bands, not promises.
- Missing or inconsistent documents that trigger repeat requests
- A large or regulated business, or several buyer groups reviewing at once
- Buyers who need bank financing
- Questions that sit unanswered because nobody owns them
- Preparing before the letter of intent, not after
- One named owner for each folder and each answer
- Releasing documents in stages through an M&A data room with permissions and a Q&A log, instead of email threads
To see where diligence fits in the full deal sequence, read the stages of the M&A process.
Five mistakes that slow down a sale
FAQ
How is a seller’s due diligence checklist different from a buyer’s?
A seller’s due diligence checklist anticipates buyer questions, while a buyer’s checklist verifies claims and uncovers risk. Each item on the seller’s list pairs a document with a check: is it signed, current, and consistent with the information memorandum and management accounts? A gap you find is a task to fix; a gap the buyer finds becomes a negotiating point that can affect price or timing. Sellers also control sequencing, deciding which documents go out before the letter of intent and which wait. See what due diligence involves.
Do I need a vendor due diligence report?
A vendor due diligence report is an independent review of your own business, commissioned by you before going to market. In a sale, “vendor” means the seller. An adviser examines areas such as finances, tax or legal position, so problems surface on your schedule rather than during negotiations. It is most useful for larger or more complex sales, or when several buyers would otherwise repeat the same work. For a small company with clean records, a checklist and data room may suffice. Ask your M&A adviser whether it fits.
Can I use email or a shared drive instead of a data room?
For a very small, low-sensitivity deal, email or a shared drive can work, but both give you little control. Attachments are hard to withdraw, links are easy to forward, and neither gives a reliable audit trail or a structured place to log buyer questions. A virtual data room lets you set permissions per bidder group, restrict downloads, release documents in stages and review activity reports. If the sale involves several bidders, confidential customer or employee data, or advisers in different locations, a data room is usually the safer choice.
What happens if due diligence finds a problem?
When due diligence uncovers a problem, there are usually three outcomes. You can fix it before closing, for example by signing a missing contract or filing an overdue return. You can disclose it and negotiate protection, such as a specific indemnity or a retention from the proceeds. Or the buyer can ask for a price reduction reflecting the cost or risk. Problems you have already found and resolved rarely lead to any of these, which is why running your own diligence first pays off. Your lawyer should guide disclosure.
Organise documents, control what each bidder sees and keep every buyer question in one place.
