Certificate for interstellar service
A certificate for interstellar service was a legal document issued by a physician certifying that the individual named in the document met the required medical criteria for service on a starship.  

Starfleet required such certification of its personnel. The certificate needed to indicate that the individual met certain cardiovascular, metabolic, and cognitive requirements.

In 2399, the retired Admiral Jean-Luc Picard asked Dr. Moritz Benayoun to issue him such a certificate in preparation for reentering Starfleet, on the basis of a remote medscan.  Benayoun noted that Picard met or exceeded all the required criteria, despite his age, but a small defect in his parietal lobe was growing worse and would eventually lead to a fatal condition. Nevertheless, Benayoun issued the certificate, noting that whatever Picard wanted to do, perhaps it would kill him before the fatal condition began to affect him. ()

Legal documents
Starfleet