Cryptographic stamp
In one sentenceAn electronic signature that the invoicing system adds to every invoice in the second phase using a certificate issued by ZATCA, to prove its source and that it has not been altered.
Simply put
The stamp is calculated from the content of the invoice itself, so any change after issuance, even to a single digit, breaks the stamp and exposes the tampering.
It is done automatically inside the system; the accountant does not add it by hand.
Example
An employee changed the amount of a simplified invoice after issuing it, so the stamp no longer matched its new content and it was rejected at reporting. The correction then had to be made with a credit or debit note.
Don't confuse it with
Cryptographic stamp identifierThe certificate is the tool issued by ZATCA; the stamp is what is applied with it to every invoice.