A passport was a document verifying the holder's identity.

The Second Doctor and Jamie McCrimmon were accosted by an immigration officer at Gatwick Airport for not having passports. (TV: The Faceless Ones)

Robin Stuart lost his passport while in Amsterdam, and was subsequently worried he would be arrested by the police and deported. (TV: Arc of Infinity)

Fitz Kreiner was born in 1936 and carried around a battered copy of his birth certificate. Miraculously, he convinced the British passport authorities in 2001 to issue him a passport on the basis of that document. He somehow convinces them that it reads 1976, rather than 1936. (PROSE: Escape Velocity)

Justicia was a star system which was used as a huge prison. Rose Tyler mentioned having gone there, and stated that she hadn't needed a passport. (TV: Boom Town)

As the TARDIS recharged from a scar in the Cardiff Rift, Rose invited Mickey over to Cardiff, claiming that she might need her passport if she ended up lost on Earth, an excuse Rose later admitted was just to see Mickey. (TV: Boom Town)

The Fourth Doctor had a galactic passport. (TV: Robot)