Australia CRN Validator
Online validator for Customer Reference Number (CRN - Centrelink) issued by Services Australia.
How does Australian CRN validation work?
The validator verifies the 9-digit base number followed by 1 uppercase control letter and calculates the Modulo 11 check letter.
Validation is performed locally in your browser without transmitting any personal data over the internet.
CRN Check Letter Calculation Algorithm
The 10th position (check letter) is obtained by multiplying the first 9 digits by weights [9, 8, 7, 6, 5, 4, 3, 2, 1]:
Sum = Σ (dᵢ × Wᵢ); Remainder = Sum mod 11; Letter = LETTER_TABLE[Remainder]
- Multiply each of the first 9 digits by decreasing weights [9, 8, 7, 6, 5, 4, 3, 2, 1].
- Sum all 9 products.
- Calculate the remainder of the sum divided by 11 (values 0 to 10).
- Map the remainder to the official letter table: 0→A, 1→B, 2→C, 3→D, 4→E, 5→F, 6→H, 7→J, 8→K, 9→L, 10→T.