How is a Belgian National Register Number structured?

It is 11 digits: the first six are the birth date as YY MM DD, the next three are a sequence number (odd for men, even for women), and the last two are a modulo-97 check.

How is the check digit calculated?

For people born before 2000, take the first nine digits as a number and the check equals 97 minus that number modulo 97. For people born from 2000 onward, prefix a 2 to the first nine digits before computing the modulo.

What does the sequence number tell you?

The three-digit sequence runs from 001 to 998 and distinguishes people born on the same day. It is odd for men and even for women, which is a quick sanity check.

Why does my number only pass on the post-2000 branch?

Both branches are valid checks; which one matches depends on the birth year. A number that passes only with the prefixed 2 belongs to someone born in 2000 or later (or registered then). The tool reports which branch matched.

Is my number sent anywhere?

No. All decoding and checksum verification happen in your browser. The number never leaves your device.

Belgium National Register Number Validator

The Belgian National Register Number (rijksregisternummer in Dutch, numéro de registre national in French) is the 11-digit identifier on every Belgian ID card and SIS card. It encodes the holder’s birth date and a sequence number, and ends in a modulo-97 check that catches typos. This free validator decodes and checks it in your browser.

How it works

The 11 digits split as YY MM DD + SSS + CC:

The first six digits are the birth date (two-digit year, month, day).
The next three are a sequence number, odd for men and even for women.
The last two are the check.

The checksum uses modulo 97. Take the first nine digits as a number N:

Born before 2000: the check must equal 97 − (N mod 97).
Born 2000 or later: prefix a 2 to those nine digits — compute 97 − ((2_000_000_000 + N) mod 97).

Because the two-digit year is ambiguous, the tool tries both branches and reports which one matched.

Example

For a number beginning 93 (born 1993), the pre-2000 branch applies: the first nine digits are read as a number, and 97 − (that mod 97) must equal the last two digits. A 2003-born holder only passes once the leading 2 is prefixed.

Notes

A passing checksum confirms the number is internally consistent, not that it belongs to a real registered person. Belgian privacy law restricts who may process this number — handle it accordingly. Everything here runs locally.