Validate a Dutch IBAN in your browser
A Dutch IBAN is the 18-character identifier used for iDEAL and SEPA payments in the Netherlands. It is compact: a 4-letter bank code from the BIC plus a 10-digit account number. This tool checks the international MOD-97 checksum and also runs the traditional 11-test as an advisory signal, all on your device.
How it works
The Dutch IBAN layout is NL + 2 check digits + 4-letter bank code + 10-digit account number.
The international checksum follows ISO 7064 MOD-97-10: move the first four characters to the end, replace letters with two-digit values (A=10 … Z=35), and require the result modulo 97 to equal 1. Because the bank code is letters, this step does real work expanding those characters.
The 11-test (elfproef) multiplies the 10 account digits by descending weights and checks that the weighted sum is divisible by 11. Modern bank-assigned numbers satisfy it, but older accounts (originally 7 digits, now zero-padded) are exempt — so the tool reports it as advisory rather than using it to decide validity.
Example and notes
The sample IBAN NL91 ABNA 0417 1643 00 has bank code ABNA (ABN AMRO) and account 0417164300. Validity is determined by the MOD-97 checksum; if the 11-test shows exempt/fail the IBAN can still be perfectly valid for a legacy account. As always, a passing checksum means the number is internally consistent, not that the account is reachable.