Adding an IBAN to your records: how do you quickly check if it's correct?

An IBAN from an email or invoice can end up in your records before anyone has properly checked it — here are four quick checks that save a lot of hassle (and sometimes thousands of euros).

You've taken on a new customer or supplier, or a colleague sends you an account number via chat. Before you know it, there's an IBAN sitting in your records that nobody has properly looked at. Most of the time, everything is fine. Sometimes it isn't. And when it goes wrong, it can quickly cost thousands of euros and a great deal of effort to get the money back — if you can at all.

In this post, we walk through the question: how do you check an IBAN before you enter it in your bookkeeping or make a payment? Without spending half an afternoon on it.

Why an IBAN check is more than a formality

An IBAN has a fixed structure and contains a built-in verification. That means a one-digit typo is picked up in nine out of ten cases as "this can't be right". Yet in practice, typos still happen — for three reasons:

• Someone manually re-types an IBAN from an email or PDF.
• An IBAN is copied and pasted with an extra space or hyphen.
• A fraudster sends a "updated account number" email and nobody checks it.

That last one has become increasingly common in recent years. Someone intercepts a genuine invoice, swaps the IBAN for a lookalike, and resends it. The rest of the invoice is correct down to the last cent. Only the account number now points to a money-mule account somewhere abroad.

What you can check in thirty seconds

Before you add a new IBAN to your records, it's worth quickly running through these points:

1. Is the structure correct? A Dutch IBAN is 18 characters (e.g. NL91 ABNA 0417 1643 00). A Belgian one is 16, a German one 22. If the character count is off, something is wrong.
2. Does the checksum add up? The digits near the start of an IBAN are a mathematical check on the rest. A good check tool calculates this instantly.
3. Does the bank match? The letters after the country code identify the bank (ABNA = ABN AMRO, INGB = ING, RABO = Rabobank, and so on). Seeing an unfamiliar bank for a supplier you've worked with for years? Pick up the phone.
4. Does the country make sense? A Dutch supplier suddenly providing an IBAN from Lithuania or Hungary isn't automatically wrong, but it is a reason to verify.

The check you often forget: name and number together

Dutch banks have an extra safety net built in: when you set up a payment, the bank checks whether the name you enter matches the IBAN. If you get a warning like "Name does not match", something is wrong. Do not click through with "proceed anyway".

In practice, we see people dismiss that warning because "the invoice looks right". That's exactly the moment to stop. Call the supplier's known number — not the number in the email — and ask whether the IBAN is correct. It takes two minutes and could save you €5,000.

An IBAN from an email: be extra cautious

Received an email in which a supplier says their account number has changed? Treat it as suspicious by default, even if the email looks professional. In practice:

• Don't reply to the email itself and don't call the number in that email.
• Look up the phone number via your own records or their official website.
• Ask whether they did in fact send a change notification.
• Note who you spoke to and when, and add that to the supplier's file.

Yes, this feels excessive for a supplier you've known for ten years. But that's precisely when fraudsters strike — because you and your colleagues are comfortable with that relationship and more likely to click "approve" without thinking.

New customer or one-off payment

A check is also worthwhile on the other side. Issuing a refund to a customer? Verify that the IBAN they provide is valid and that the name matches. That prevents you from sending money to the wrong account and then having to chase it down.

For larger amounts: make a small test payment first — say, one cent — and ask for confirmation. Old-fashioned? Yes. Effective? Absolutely.

Clear agreements within your team

Technology is only half the story. The other half is what your team agrees to do. A few things that work well in SMB settings:

• New supplier or changed IBAN → always checked by a second pair of eyes.
• Above a certain amount (e.g. €1,000) → always verified by phone.
• Payments are never processed "quickly" outside the regular payment run.
• When in doubt: wait one day. Genuine suppliers will understand.

These rules may seem bureaucratic, but they target exactly the moments when fraud works: urgency, authority ("the boss asked for it"), and the familiarity of a long-standing relationship.

What you can do right now

Pick up an invoice sitting on your desk today and run through the four check points above. Find something that doesn't add up or doesn't feel right? You now have a concrete reason to call.

Just want to quickly verify the structure and checksum of an IBAN? Use our IBAN checker — paste the number in and immediately see whether it's formally valid and which bank it belongs to. It works the same way for a VAT number, by the way: a quick check before you add a new supplier saves a lot of digging around later.