Kia ora koutou,
I would like to draw your attention to an update to HISO 10046:2023 Consumer Health Identity Standard.
The latest revision includes an update to the check digit algorithm used for the new NHI numbering format. This update was made to mitigate an unacceptable risk of character substitution detection failures that were identified with the former approach. To address this, we have changed the check digit algorithm to use a modulus 23 operator, rather than a modulus 24 operator. This change remediates the character substitution failure concerns.
For further information and for a copy of the updated standard, please see
https://www.tewhatuora.govt.nz/publications/hiso-100462023-consumer-health-identity-standard/