Burgerservicenummer
Netherlands · Individuals
Paste or type the number — punctuation is optional.
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What this check does — and what it cannot do
This tool checks the number's structure and its check digit, using the published algorithm for that document. A number that passes is well formed: it is arithmetically consistent and could have been issued.
It cannot tell you whether the number was actually issued, whether it is active, or who it belongs to. Only the issuing tax authority can confirm that, through its own lookup service. Treat a passing result as "worth submitting", never as proof of identity.
Calculated in your browser. Nothing you enter is sent anywhere.
Only about one nine-digit number in eleven is a possible BSN
The Dutch elfproef weights the digits 9, 8, 7, 6, 5, 4, 3, 2 and then −1 for the last one, and the total must divide by eleven. Counting across the space, 9.08% of all nine-digit strings satisfy it — roughly one in eleven, exactly as a modulo-11 test implies. A number picked at random is almost certainly not a valid BSN.
How it works
- Applies the elfproef weights and checks the total is a non-zero multiple of eleven.
- Rejects all-zero input, which passes the arithmetic but is never issued.
- Reports which test was applied, so the result can be reproduced by hand.
9×d₁ + 8×d₂ + 7×d₃ + 6×d₄ + 5×d₅ + 4×d₆ + 3×d₇ + 2×d₈ − 1×d₉ valid when the total is divisible by 11 and is not zero
Worked example
Why the last digit is subtracted rather than added.
- the first eight digits take descending weights from 9 down to 2
- the ninth takes weight −1, which is what makes it a check digit rather than data
- the whole weighted total must be a multiple of eleven
- if it were +1 the last digit could not uniquely fix the total
- measured across the space, 9.08% of nine-digit strings pass
A single arithmetic test over all nine digits, with no separate check position. The last digit is ordinary data that happens to be constrained.
Reading the result
- A passing elfproef means well formed, not issued. The BSN register is the only authority on whether a number belongs to anyone, and this page has no access to it.
- The BSN is tightly regulated in the Netherlands. Only organisations with a statutory basis may record it, so if a form asks for yours without a clear legal reason, that is worth questioning rather than answering.
- No generator is offered. This identifies a person, and a well-formed BSN is exactly what a fraudulent application needs — unlike a company number there is no legitimate reason to synthesise one.
Common questions
- Why does modulo 11 reject so many numbers?
- Because it partitions the space into eleven classes and accepts only one of them. That is the point: the nine-tenths it rejects are the room the checksum uses to notice mistakes.
- Does a valid BSN prove the person exists?
- No. It proves the digits are arithmetically consistent, which catches typing mistakes and nothing else. Identity has to be established some other way.