As soon as the ship comes through, its signature is registered
and the
fees debited against their account, if they have one at the
station. If not,
the incoming person is asked for payment before being allowed onto
the
station. In some cases, as with transports, corporations buy jump
gate access
in bulk, and then assign the routes to their various transports.
(Believe it
or not, this actually comes up in dialogue in "Midnight.")

jms