The government agency responsible for the registration and numbering of vehicles is the Directorate General of Traffic.

In August 2022 the three-letter counter reached the end of the L-series, and began the M-series, starting MBB.

The plates themselves are white with black characters, front and back, with a blue strip on the left containing the 12 stars of the flag of Europe and the country identifier E (for España).

Today, there are a few rare cases where the blue EU country identifier strip is also carried, as plates are reissued in new format but with the same number sequence when deteriorated or lost.

No "counter" series used the consonants Q and R (and Q has never been allowed in any way, the apparent reason for this being its resemblance to the vowel O and the digit 0), while two-letter combinations ending in the vowels A, E, I and O were also forbidden, apparently to avoid the forming of potentially offensive Spanish words when combined with some province codes (such as MA-LA, meaning "bad one", or CU-LO, meaning "arse").

This system lasted until January 2000, by which time Madrid was running out of registrations again, its "counter" reaching series ZX.

Under this system, plates usually consisted solely of black characters on white, though the blue EU country identifier strip became an option in the 1990s.

Both systems were susceptible to problems with rivalries between regions, that caused trouble for drivers travelling out of their provinces or trying to sell their vehicles second-hand.

The second system was also affected when the major languages of Spain were co-officialized, with the renaming of some provinces resulting in mismatches between the name and the code.

La Rioja code LO (from its former name after its capital Logroño) was finally slated for replacement with LR on the same day that the current system entered use.

The tourist plates begin with the prefix P signifying provisional, usually issued to vehicles for export or until the registration process has been completed.