NI is not ID for working. It's a tax identifier.
The ID for working system is https://www.gov.uk/prove-right-to-work , with its digital ID "share code" https://www.gov.uk/view-right-to-work
(what does the digital ID scheme add to this again?)
The ID for working system is https://www.gov.uk/prove-right-to-work , with its digital ID "share code" https://www.gov.uk/view-right-to-work
(what does the digital ID scheme add to this again?)
The prove right to work is a slightly newer thing thats additional
Previously you could use proof of British nationality or a physical biometric residence card - but they've been replaced by the digital share code system (which tbh hasn't been too bad)