What this check does — and what it cannot do

This tool checks the number's structure and its check digit, using the published algorithm for that document. A number that passes is well formed: it is arithmetically consistent and could have been issued.

It cannot tell you whether the number was actually issued, whether it is active, or who it belongs to. Only the issuing tax authority can confirm that, through its own lookup service. Treat a passing result as "worth submitting", never as proof of identity.

The generator produces numbers that satisfy the same checksum, for filling forms while developing and testing software. They are arithmetic, not records: they are not drawn from any register and do not correspond to a real holder. No generator is offered for the US Social Security Number.