How do I prove the validity of the TCP certificate?

The operator shall retain, and make available on request, the cabin crew certificate, roster, training and checking records pertaining to his type or variant of aircraft qualifications, unless such records are maintained by the operator employing his services and can be made available promptly on request to a competent authority or to the operator.

Regulation (EU) 1178/2011: CC.GEN.025(b).