Belgian National Register Number Validator (NN / NISS)
Validate structural compliance and check digits of Belgian National Numbers.
About Belgian National Number Validation
Validation sanitizes input and evaluates birth date coherence, gender sequence counter, and Modulo 97 check digits.
Natively supports numbers issued to individuals born in both the 20th and 21st centuries.
Anatomy & Structure of Belgian National Number
The Belgian NN consists of 11 decimal digits regulated by IBZ:
| Position | Field | Length | Meaning & Rule | Example |
|---|---|---|---|---|
| 1 to 2 | Birth Year | 2 digits | Last two digits of the individual's birth year | 85 |
| 3 to 4 | Birth Month | 2 digits | Month of birth (01 to 12) | 07 |
| 5 to 6 | Birth Day | 2 digits | Day of birth (01 to 31) | 30 |
| 7 to 9 | Counter & Gender | 3 digits | Daily sequence counter (Odd = Male; Even = Female) | 123 |
| 10 to 11 | Check Digits | 2 digits | Modulo 97 check digits (with '2' prefix for births from 2000) | 45 |
NN Calculation & Validation Algorithm (Modulo 97)
NN validation distinguishes centuries through the Modulo 97 prefix rule:
DV = 97 - ((prefix2? + Base9) mod 97)
- 1. Sanitize input by removing dots, slashes, and hyphens.
- 2. Validate that the string consists of exactly 11 numeric digits.
- 3. Test the 20th-century calculation: 97 - (Base9 mod 97) compared against the last 2 digits.
- 4. If it doesn't match, test the 21st-century calculation: 97 - (BigInt('2' + Base9) mod 97).
- 5. If either formula matches the check digits, the number is authentic.