Once issued, a standard authorisation can last for a maximum of 12 months, but every effort should be made to ensure that it is in place for as short a time as possible.
Ar ôl i awdurdodiad safonol gael ei roi, gall bara am 12 mis ar y mwyaf, ond dylid gwneud pob ymdrech i sicrhau ei fod yn ei le am gyn lleied o amser â phosibl.