ICS-CERT receives information from certification bodies to ensure the Certification is valid with a special QR Scan logo on every authentic document
ICS-CERT receives information from Accreditation Bodies to ensure the Certification Bodies are accredited to issue certifications to that standard with a text-link of the authentic on the document which can be seen as pdf on ics-cert.org
You can send a mail directly to verify@ics-cert.org with including document number, scanned document the check the document is legit or not.
The three information sources enable accurate verification of accredited certification.