Dutch BSN Validator

BSN: the Dutch citizen number and the "elfproef" 11-test

The BSN (Burgerservicenummer) is the 9-digit citizen service number that identifies every resident of the Netherlands across government, healthcare and tax systems. Its integrity is protected by the elfproef ("eleven test") — a weighted checksum that catches typos. This tool runs that check on the nine digits.

The elfproef multiplies the digits by descending weights 9, 8, 7, 6, 5, 4, 3, 2 and the last digit by −1; the total must be divisible by 11 (and the number can't be all zeros). The negative weight on the final digit is the distinctive twist that separates the BSN from the older sofinummer rules.

The elfproef, step by step

• Weights: 9 8 7 6 5 4 3 2 −1 across the nine digits.
• Sum: multiply each digit by its weight and add.
• Rule: valid only if the sum is a multiple of 11.
• Exclusion: 000000000 is rejected even though it passes arithmetically.

Where it matters

• Government & DigiD: the BSN is the key to Dutch e-government and the DigiD login.
• Healthcare & tax: doctors, the Belastingdienst and employers all use it.
• Privacy-sensitive: handling a BSN is legally restricted — only specific parties may store it.
• Mock data / testing: the elfproef lets you generate valid test BSNs without real data.

Common pitfalls

• Note the −1 weight: the last digit is subtracted, not added — a common implementation bug.
• Leading zeros: BSNs can be 8 digits historically; pad to 9 and store as a string.
• Checksum ≠ issued: passing the elfproef doesn't mean the BSN belongs to a real person.
• Don't store casually: Dutch law restricts who may process a BSN.

FAQ

What is the elfproef? The "eleven test": a weighted sum (9…2, then −1) that must be divisible by 11.

Is the BSN the same as the old sofinummer? The BSN replaced and extended the sofinummer in 2007; the number can be the same but the framework differs.

Can I just store anyone's BSN? No — processing a BSN is legally limited to authorised organisations.