What is the format of a Dutch IBAN?

A Netherlands IBAN is always exactly 18 characters: the 2-letter country code NL, two check digits, four uppercase letters that identify the bank (called the BBAN bank code), and ten digits that form the account number. Example: NL91 ABNA 0417 1643 00.

How does the MOD-97 checksum work for Dutch IBANs?

The first four characters (NL + check digits) are moved to the end of the string. Each letter is replaced by its numeric equivalent (A=10, B=11 up to Z=35). The resulting long integer is divided by 97 — a valid IBAN always leaves a remainder of exactly 1. The tool computes this remainder progressively, digit by digit, so no large-integer arithmetic is needed.

Can a number pass the MOD-97 check but still be rejected?

Yes. This validator applies four independent checks in order: NL country code, exactly 18 characters, BBAN structure (four letters then ten digits), and finally the MOD-97 checksum. A fabricated number can accidentally satisfy the checksum while failing the length or BBAN structure check. Each failure gives a specific message explaining the exact problem.

Does passing all four checks confirm the account is real?

No. The MOD-97 algorithm and structure checks confirm the IBAN is internally consistent and correctly formed. They cannot verify whether the account exists, is open, or belongs to a particular person — only DNB (De Nederlandsche Bank) or your bank can do that. Think of it as a spell-checker for the number, not a directory lookup.

Is it safe to enter a real IBAN into this tool?

Yes. The entire validation runs as JavaScript inside your browser. The IBAN is never sent to any server, never logged, and never stored. The page makes no network requests during validation. You can verify this in your browser developer tools under the Network tab.

Netherlands IBAN Validator

Q: What does the 4-letter bank code mean?

Characters 5 to 8 of a Dutch IBAN (positions 5-8 in 1-indexed notation) are a BIC-derived bank identifier. For example ABNA identifies ABN AMRO, RABO identifies Rabobank, and INGB identifies ING Bank. The validator recognises 14 major Dutch institutions and displays the name alongside the code. If the bank code is valid structurally (four letters) but not in its list, the tool still validates the number — the list is illustrative, not exhaustive.

The Netherlands IBAN (Internationaal Bankrekeningnummer) is the standard Dutch bank account identifier used for all SEPA credit transfers, direct debits, and international wire payments. Every Dutch IBAN is exactly 18 characters long and carries a built-in four-layer structure that makes it possible to detect transcription errors before a payment is submitted. This validator applies all four checks — country code, total length, BBAN composition, and ISO 7064 MOD-97 checksum — entirely inside your browser. No data ever leaves your device.

The anatomy of a Dutch IBAN

A Netherlands IBAN is assembled from four mandatory sections placed one after another without separators (spaces are cosmetic only):

Section	Length	Content	Example
Country code	2 letters	Always “NL”	NL
Check digits	2 digits	ISO 7064 MOD-97 protection value	91
Bank code	4 letters	BIC-derived bank identifier	ABNA
Account number	10 digits	Domestic account reference	0417164300

Put together: NL91 ABNA 0417 1643 00 — one of the two canonical Dutch test IBANs published in the SWIFT IBAN registry. The grouped-of-four display is convention only; the 18 underlying characters are what actually matter.

How the MOD-97 checksum works

The ISO 7064 MOD-97-10 algorithm is the same for every IBAN in every country. Starting from the full 18-character Dutch IBAN, the steps are:

Move the first four characters (NL + the two check digits) to the end of the string, giving a 18-character rearranged sequence that starts with the bank code.
Replace every letter with its numeric equivalent: A becomes 10, B becomes 11, all the way to Z which becomes 35. Because “NL” maps to “2321”, the digit string expands slightly beyond 18 characters.
Treat the entire digit string as one large integer and divide by 97. A structurally correct IBAN will always leave a remainder of exactly 1.

To avoid floating-point overflow the validator processes the digit string one character at a time, updating a running remainder: r = (r * 10 + digit) mod 97. This keeps the working value between 0 and 96 throughout.

The BBAN bank code

Positions 5 to 8 of the IBAN hold a four-letter bank identifier derived from the bank’s BIC (Bank Identifier Code). The validator recognises 14 major Dutch institutions including ABN AMRO (ABNA), Rabobank (RABO), ING Bank (INGB), bunq (BUNQ), Triodos Bank (TRIO), and Knab (KNAB). When the code is recognised the bank name is shown alongside the letters. If the code is structurally valid — four uppercase letters — but not in the display list, the IBAN is still fully validated; the list is illustrative, not exhaustive, because smaller banks and new entrants can register any available four-letter code from the SWIFT BIC registry.

Worked example

Validate NL91 ABNA 0417 1643 00:

Strip spaces: NL91ABNA0417164300 (18 characters — correct)
Bank code ABNA — four uppercase letters (passes BBAN check)
Account 0417164300 — ten digits (passes BBAN check)
Rearrange: move NL91 to the end — ABNA0417164300NL91
Expand letters: A=10, B=11, N=23, A=10, N=23, L=21 giving the digit string 101110041716430023211… followed by 91
Compute the full string mod 97 progressively — result is 1 (passes)

The result is a valid Dutch IBAN. The check digits 91 were specifically chosen when the account was issued so that this final remainder works out to 1.

What this validator does NOT check

Structural validity is not the same as account existence. The four checks in this tool confirm the IBAN is correctly formed — they detect the majority of transcription errors, swapped digits, and mistyped bank codes. They cannot tell you whether the account is open, whether the named bank still operates, or whether the IBAN has been closed. For payment confirmation, contact your bank or use SEPA’s pre-validation API (available to payment service providers through the ECB’s payment processing framework).