Blog · Controls and audit

How to onboard a new supplier

Published 8 October 2026 · 5 min read

Onboarding a supplier means collecting their details once, checking the ones that move money, and telling them how you buy. Get the legal name, tax numbers, order email and bank details. Confirm the bank details by phone, on a number you already hold. Keep one record per supplier. A short call at the start costs far less than a payment sent to the wrong account.

What to collect

Ask for everything in one go, in writing, before the first order. A simple form you send to every new supplier works well, because it asks the same questions each time and leaves a record of the answers.

• Legal name: the name the business is registered under, which may differ from the name on its van or website.
• Registration number: the company registration number, if the business is registered.
• VAT number: if they are VAT registered. If they say they aren’t, note that too, so nobody later reclaims VAT on their invoices by mistake.
• Address: the registered address, and the trading address if it is different.
• Order email: the address that receives purchase orders. Ask for a shared mailbox rather than one person’s inbox where you can.
• Contact for queries: a name and phone number for questions about orders and invoices.
• Bank details: account name, bank, account number and branch or sort code, on the supplier’s letterhead or a bank confirmation letter.

The checks that matter

Most supplier fraud doesn’t need clever technology. Someone sends an email that looks like it came from a supplier, says the bank details have changed, and waits. The checks below close that gap.

• Verify bank details by phone. Call the supplier on a number you already hold, from their website, an earlier invoice or a contract, never the number in the email that sent the details. Ask them to read the account number back to you. Do the same every time bank details change.
• Check the VAT number. Look it up on the public VAT register where your country has one, and make sure the name it returns matches the legal name you were given.
• Match the names. The trading name, the legal name and the name on the invoice should belong to the same business. If the invoice names a different company, ask why before anything is paid.
• Separate the jobs. The person who adds or changes bank details shouldn’t be the person who approves payments to that supplier.

Information, why it matters and how to check it

Use this as the checklist behind your supplier form.

When a once-off supplier is fine

Not every purchase needs a full onboarding. A once-off supplier is reasonable for a small purchase you don’t expect to repeat, such as an emergency repair away from the office, paid by card or against a single invoice.

Set the supplier up properly once you buy from them a second time, once the spend passes the amount your purchasing policy sets, or as soon as you will pay them by bank transfer. A transfer to an unchecked account is exactly the payment the checks above exist to protect.

Keep one record per supplier

Duplicate supplier records are how invoices get paid twice. The same business ends up as “Acme Ltd”, “ACME Limited” and “Acme Plumbing”, each with an invoice that looks new.

Before adding a supplier, search for the registration and VAT numbers as well as the name. Give each supplier one code and keep it. When you stop buying from a supplier, retire the record rather than deleting it, so its history stays with it. There is more on this in how to stop duplicate supplier payments.

What to tell the supplier

Onboarding runs both ways. A new supplier needs to know how you buy, or their invoices will arrive in a form you can’t match to anything.

• Quote the purchase order number on every invoice. An invoice without one waits until it is sorted out.
• Invoice the entity named on the order. If you buy through more than one company, the invoice must name the one on the purchase order.
• Only act on a purchase order. A phone call or a chat message is not an order.
• Send bank changes in writing, and expect a call. Say up front that you will phone to confirm any change.

Onboarding a supplier, step by step

Run the same steps for every new supplier, so nothing depends on who happens to do it.

1. Search your existing records for the name, registration number and VAT number, so you don’t add the same supplier twice.
2. Send the supplier your form asking for the details listed above.
3. Check the registration and VAT numbers on the public registers, and that the names match.
4. Phone the supplier on a number you already hold to confirm the bank details.
5. Have a second person review the record before it is used for payment.
6. Add the supplier to your list with one code, the order email and the contact for queries.
7. Send the supplier your buying rules: the PO number on every invoice, the right entity, and how bank changes are confirmed.
8. Write the first purchase order and check the supplier received it.

Questions

What information do I need from a new supplier?

Their legal name, company registration and VAT numbers if they have them, address, the email that receives orders, a contact for queries, and bank details. Get it in writing before the first order.

How do I check a supplier’s bank details are genuine?

Phone the supplier on a number you already hold, not one given in the email with the bank details, and ask them to confirm the account number. Repeat the call whenever the details change.

Do I need a supplier’s VAT number?

If they are VAT registered, yes: it shows on their invoices and affects whether you can reclaim the VAT. Check it on the public VAT register, and confirm the treatment with your accountant.

When should a once-off supplier become a regular supplier?

When you buy from them a second time, when spend passes the limit in your purchasing policy, or as soon as you will pay them by bank transfer. Until then, keep the purchase small and the payment method low risk.