Important: The VERIFYSIG command and VerifySignature functions will verify that the signature (Sello) in the XML document was created by the owner of the private key corresponding to the X.509 certificate (Certificado) and that the correct digest has been used according to the SAT version number.

Nothing else is checked: dates, certificate expiry, certificate revocation, RFC number, validity of version as at date of issue. The SAT validator sites may do extra tests that indicate a Comprobante is invalid even if it passes the FirmaSAT tests.