A docking permit was a legal document granting permission for a vessel to dock at a space station. They were issued by a government agency with jurisdiction over the relevant location. Such permits could also detail the vessel's personnel and any auxiliary space vessels.
One such example was Ledos Port Control, which in 2377 granted the USS Voyager a docking permit to dock at a space station in orbit of Ledos. A Ledos official was able to correctly identify Tom Paris as being a crew member of Voyager due to the docking permit, after he had violated Piloting violation 256 of Ledosian law. (VOY: "Natural Law")