IBAN checker and validator

How the IBAN checksum works

An IBAN (International Bank Account Number) is a country code, two check digits and the BBAN, the national account number. The ISO 13616 standard sets the exact length for each country.

1. Move the first 4 characters to the end 2. Replace each letter with a number (A = 10 … Z = 35) 3. Divide the long number by 97: the remainder must be 1

This catches every single-character typo and most swaps of two neighboring characters. It proves the IBAN is well formed, not that the account exists.

IBAN length by country

The tool covers more than 75 countries. The United States does not use IBANs: US wire transfers use a routing number and an account number.

When you need an IBAN

If you send or receive money from Europe, the UK, the Middle East or Brazil, the other side will ask for an IBAN, often with a SWIFT/BIC code for banks outside the SEPA area.

• Payments in euros inside Europe: the IBAN alone is enough.
• Payments from the US: a wire needs the IBAN plus the receiving bank's SWIFT/BIC code.
• Typo risk: a wrong IBAN can delay a wire for days and cost a return fee. Always check it first.

Use the SWIFT/BIC decoder to read the bank code that goes with it.

IBAN validator: the checksum step by step

An IBAN check follows a precise method defined by ISO 13616. Here are the four steps.

1. Remove the spaces and make all letters uppercase.
2. Move the first four characters to the end.
3. Replace each letter with a number: A is 10, B is 11, up to Z which is 35.
4. Divide the big number by 97. If the remainder is 1, the IBAN is valid.

For example, the sample IBAN GB82 WEST 1234 5698 7654 32 passes this rule. So an error in a single digit almost always breaks the check.

IBAN validator: length by country

Each country sets an exact length. If the character count is off, the IBAN is wrong, even with a correct check digit pair.

So when you copy an IBAN, count the characters before you confirm a transfer.

IBAN validator: caution and fraud

A format check does not prove the account belongs to the right person. Still, it catches typos, which cause most rejected transfers.

• Verify an IBAN from an invoice through a trusted channel, especially if a supplier changes accounts.
• Call the supplier at a known number before you send a large payment.
• Share your IBAN only with people or companies you trust.

To go further, decode a bank identifier with the SWIFT code decoder, secure your accounts with the password generator and check a number with the phone number lookup before you call back.

Before you wire money: useful habits

Before you send money, spend thirty more seconds. First, reread the characters one by one. Next, compare them with the original document. Then run the check here. Finally, send a small test amount if the sum is large.

If you hesitate, call the recipient. A phone call settles a doubt faster than a misdirected payment. Also, keep the payment receipt. Still, never post it online, because it holds sensitive data.

Common mistakes when you copy an account number

The most common mistakes are simple. First, swapping two digits breaks the check. Next, a stray space is harmless, because the tool removes it. Finally, typing the letter O instead of a zero is a classic mix-up. So always reread the number at the end, and never type it from memory.

Also, if the tool says the length is wrong, check the first two letters. A wrong country code changes the expected length, and the number then looks invalid even though the rest is right. Then compare it with the original once more.