The system began in 1937 with AA-10-00, then went on to 00-00-AA and recently changed over to 00-AA-00. When this sequence comes to an end, it will be replaced by the sequence AA-00-AA.
A list of the first registration numbers issued each month since March 1992 (starting with 00-01-AA) is available at the Automobile Association of Portugal.
The "P" denominates Portugal and was added in 1992 with the EU flag on the left of the plate. In 1998, a yellow (previously pink on some vehicles) band on the right side was added with the month and year in which the car was first registered.