Cert (noun)

1. A document or certificate that serves as proof of a particular fact or status.
2. A document that serves as official proof of a certain qualification or achievement.

Origin:

Shortened form of certification.

Examples:

1. She showed her cert to prove that she was a certified yoga instructor.
2. I have a cert of completion for the course.
3. The cert of authenticity for the painting was issued by the museum.
4. The cert of insurance was required before the project could begin.
5. The cert of inspection was needed before the building could be occupied.