A due diligence checklist for choosing a business supplier

Due diligence is a way to resolve the questions that could change your decision, not a demand for every document a supplier owns. Start with the service you need, the likely cost of failure and the information you already have. Then check identity, capability, delivery arrangements and exit terms using the same core questions for each candidate.

Confirm who you would be buying from

Record the legal name that will appear on the agreement, the contact address and the person authorised to agree the work. Check that the proposal, invoices and contract identify the same entity. If the company uses trading names or partners, ask which organisation is responsible for delivery and support.

A public profile, award or directory entry can guide research, but it is not a substitute for checking the underlying record or speaking to the supplier. Keep a note of when you made each check because details can change.

Test capability against your actual brief

Ask for one or two relevant examples and the supplier's specific role in them. Similarity might mean the same audience, technology, project size or operational challenge rather than the same sector. Ask who will carry out the work, how it is reviewed and what happens if a key person becomes unavailable.

For a complex project, request a short explanation of delivery stages and risk points. Can the company describe how it will handle an unexpected delay or an unclear requirement? An answer that identifies assumptions is often more useful than an unqualified promise.

Check the working relationship and the exit

Compare how suppliers communicate progress, approve changes and escalate problems. Clarify support hours and what response times mean. Check who will control accounts, data and working files during the project and at handover. Review payment milestones, renewal dates and cancellation arrangements before the final decision.

Use a simple evidence log with columns for question, supplier answer, supporting document, date and follow-up. Mark statements you have not verified. If reviews are part of your research, the review evidence table guide can help you avoid counting the same anecdote twice.

Make the checks proportionate

A modest one-off assignment does not need the same process as a long contract involving sensitive information. Decide in advance which missing answers would stop the purchase and which can be clarified during onboarding. The goal is a defensible decision, not a stack of paperwork.

Decide in advance what would change your mind

Before the final meeting, write down the two or three findings that would stop the purchase, such as unclear ownership of a critical account or no workable support route. Separately list questions that need a written answer but would not necessarily rule the supplier out. This distinction keeps the process proportionate. It also helps you explain a decision if one candidate has a stronger presentation while another has clearer evidence of delivery and a safer handover.

Frequently asked questions

Is due diligence only for large organisations?

No. A small business can use a short checklist focused on identity, relevant work, price, support and exit. The depth should match the risk.

Should I ask for references?

For material projects, references can help. Ask about work similar to yours and remember that a supplier is likely to select satisfied clients.

What if a supplier refuses to answer a key question?

Explain why the answer matters and offer a reasonable way to provide it. If it remains unresolved, record the risk and compare alternatives.