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Your real notice looks like a fraud attempt
An email arrives in a customer's accounts payable inbox. It is from a supplier they know, on the usual letterhead, and it says: we have changed banks, please use these new details from now on. That is what your genuine notice will look like. It is also, word for word, what the most common payment fraud looks like.
The FBI's Internet Crime Complaint Center recorded 2.77 billion dollars in business email compromise losses in 2024, and changed bank details are the standard play. Your customers have been trained to distrust exactly this message, and they are right to.
So a good notice is not one that sounds convincing. Fraudsters sound convincing. A good notice is one your customer can check without having to trust the message it arrived in.
What your customer's finance team will do with it
Write the notice for the person who has to process it. A careful finance team will not act on the letter alone. Expect some or all of these, and make each one easy.
| What they will do | How to make it easy |
|---|---|
| Call you on a number they already hold | Do not offer a new phone number for checking. Tell them to use the one on file, and brief whoever answers it |
| Ask for proof from the bank | Attach a bank confirmation letter or a voided cheque showing the account name |
| Check the account name matches your legal name | Use the exact legal name on your invoices, and explain any difference before they have to ask |
| Have a second person approve the change | Give enough notice that their approval process is not rushed |
| Send a small test payment first | Offer to confirm receipt of a test payment the same day |
| Hold payments until the change is confirmed | Keep the old account open for an overlap period so nothing bounces |
Before you write the letter
1. Give notice early. Thirty days before the first payment is due to the new account is a reasonable minimum. Short notice is itself a warning sign.
2. Keep the old account open for a while. Payments already in progress will still land, and nobody has to act in a hurry.
3. Send it from a named person your customer already deals with, to a named person in their finance team, and copy your usual contact there.
4. Brief your own team. Whoever answers the phone number your customers hold must know about the change and be able to confirm the new details. A callback that reaches someone who has never heard of it does real damage.
5. Decide how customers will check the letter. A proof link or a delivery channel they can verify is better than a signature block.
6. Change everything on the same day: invoice templates, your customer portal, remittance advice and the payment page on your website. Mixed signals look like fraud.
7. Never ask for urgency or secrecy. Do not follow up with pressure. Those are the marks of the real thing's imitation.
The letter
Put it on your letterhead, as a PDF, and fill in every bracket. Keep the wording plain. The paragraph on how to check the letter is the part that matters most, so do not cut it.
[Your company letterhead]
[Date]
[Customer name]
For the attention of: [Named contact], Accounts Payable
Change of bank details for [Your company legal name]
Dear [Name],
From [effective date], [Your company legal name] will receive payments
into a new bank account. Our company name, registration number, address
and the people you deal with have not changed.
Please use the details below for invoices due on or after [effective date].
Account name: [Exact legal name on the account]
Bank: [Bank name and branch address]
Account number: [Account number or IBAN]
Sort code, routing number or SWIFT/BIC: [Code]
Currency: [Currency]
Our previous account, ending [last four digits], stays open until
[date], so payments already in progress will still reach us.
How to check this letter
Please do not act on this letter alone.
1. Call the phone number you already hold for us, not a number shown
in this letter or in the message it came with. Ask for [name or
team] and read the new details back to us.
2. Check that this file is the one we issued. Drop it on
[proof link]: the page compares it with the record we made when we
sent it, and nothing is uploaded.
3. A confirmation letter from our bank is attached.
We will never ask you to change these details by email alone, to act
urgently, or to keep a change confidential. If you receive a message
that does, please call us on the number you already hold.
Yours sincerely,
[Name]
[Title]
[Your company legal name]
The covering email
Keep the account details out of the email itself. An email is easy to imitate and easy to alter in a compromised mailbox, and a customer who gets used to reading bank details in email bodies is easier to fool next time.
Subject: [Your company]: change of bank details from [effective date]
Hi [Name],
We are changing banks. From [effective date], payments to
[Your company legal name] should go to a new account.
The formal letter with the new details is attached [or: is in our
evidence room, link below]. I have deliberately left the account
details out of this email.
Before you update anything, please call us on the number you already
have for us and confirm the details with [name or team]. The letter
also explains how to check that the file is genuine.
Nothing else has changed: same company, same contacts, same terms.
[Name]
[Title]
Send it so the customer can check it
The weak point of any letter is the journey. An attacker who can read a mailbox can replace the attachment, or send a second "corrected" letter a week later. Two things close that gap.
Record the letter's fingerprint before it leaves. Your browser computes a SHA-256 fingerprint of the final PDF and Invoance signs it with your organization's key and records the time. That gives you the proof link in the template: anyone holding a copy can drop it on the page and see match or no match, with no account and nothing uploaded. A swapped or edited letter does not match.
Deliver it through an Evidence Room. Add the letter and the bank's confirmation, and name each customer contact as a recipient. The files are encrypted in your browser before upload. Each recipient opens their own link, asks for a 6-digit code that is sent to the address you named, and needs no account. Their device checks each download against your fingerprint before saving it, and every open and download goes into a signed log. You can see which customers have received the notice, and show it later.
This does not replace your customer's callback, and it should not. Invoance does not check bank accounts or who owns them. It shows that the letter in front of your customer is the one you issued. The emailed code is as strong as the recipient's inbox, unless the room requires a passkey.
What not to do
Do not announce the change only in the footer of an invoice. Customers will miss it, or worse, will learn to accept changes that appear that way.
Do not send the notice from a new email address or domain, or from a general mailbox the customer has never seen.
Do not put a new phone number in the letter as the way to verify it. A fraudster would do the same.
Do not ask a customer to skip their own process because the two of you have worked together for years. Thank them for running it.
Do not change bank details and contact details in the same month if you can avoid it. Each change makes the other harder to check.
If a customer receives a fake notice in your name
Sooner or later a customer will forward you a "change of bank details" letter you never sent. Having a known way of sending real ones makes this a short conversation: you can say that genuine notices arrive only through your room or with a proof link, and that any copy can be checked on the proof page.
Ask them not to pay, and to call you on the number they hold. Ask for the message with its full headers, so you or your IT team can see where it came from. If money has already gone, they should call their bank immediately and report it, since the chance of recovering funds falls quickly. Then tell your other customers that a fake is circulating, through your usual channel, and check whether one of your own mailboxes has been compromised.