HesapHanem

BSN Validator (Netherlands)

Enter a Dutch BSN to check it against the eleven-test.

How it is calculated

The tool removes everything that is not a digit (spaces, dots, dashes and even letters), so "111 222 333" works. An 8-digit number gets a leading zero to make 9 digits. Anything with fewer than 8 or more than 9 digits is marked not valid straight away. Then the nine digits d₁…d₉ are weighted: sum = 9·d₁ + 8·d₂ + 7·d₃ + 6·d₄ + 5·d₅ + 4·d₆ + 3·d₇ + 2·d₈ − 1·d₉. The number passes the eleven-test when sum mod 11 = 0. The remainder is shown so you can see how far off a failing number is.

The all-zero number 000000000 is also rejected, although its sum is 0. This only checks the internal checksum of the digits. It cannot tell whether the number was ever issued to a person, and it does not check the owner's name or birth date.

Worked example

Take 111222333. Weighted digits: 9×1 + 8×1 + 7×1 + 6×2 + 5×2 + 4×2 + 3×3 + 2×3 − 1×3 = 9 + 8 + 7 + 12 + 10 + 8 + 9 + 6 − 3 = 66. Now 66 ÷ 11 = 6 exactly, so the remainder is 0 and the length is 9 digits. The tool reports the number as valid (1). Changing the last digit to 4 (111222334) gives a sum of 65 and a remainder of 10, which fails.

Try this example →

Common mistakes

  • Treating "valid" as "real". A number that passes the eleven-test only has a consistent checksum; many passing numbers have never been issued to anyone.
  • Adding extra digits by accident, for example a country code or a second copy of a digit. Anything beyond 9 digits is rejected, while letters such as NL are simply dropped.
  • Typing 8 digits and expecting an error. Some older numbers are written with 8 digits, and the tool adds the leading zero itself.
  • Using the same check for the Dutch A-number, a phone number or an IBAN. Those have different rules; this test is specific to the BSN.
  • Reading a small remainder as "almost correct". A remainder of 1 or 10 does not mean one digit is off by one; the checksum only says whether the sum is divisible by 11.

About this calculator

The Dutch burgerservicenummer (BSN) is validated with the official eleven-test (elfproef): each of the nine digits is multiplied by a fixed weight (9, 8, 7, 6, 5, 4, 3, 2, and −1 for the last digit), the products are summed, and the number is valid only if that sum is exactly divisible by 11.

Because the eleven-test catches the vast majority of typos and transposed digits, it's built into the number itself as a self-check rather than relying on a separate lookup. Dutch employers and HR/payroll administrators, banks, and software developers building registration or KYC forms for the Netherlands use this check to reject an invalid BSN at data entry, before it ever reaches a government system like the Belastingdienst or UWV.

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Comments (1)

  • Editorial team

    Passing the 11-test shows the digits are internally consistent, not that the number was ever issued. The weights make any swap of two neighbouring different digits fail, which catches many typing slips. Eight-digit numbers are padded with a leading zero. A real BSN is personal data, so use made-up test numbers such as 111222333 when you only want to see the check work. Which kind of form needs this check?

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