Many UK nationals who were resident in Spain before Brexit are worried by reports that Spanish border police are stamping their passports when they enter and leave Spain. According to the official rules, UK nationals who can prove their residential status either with the green A4 sized paper or new TIE card should not have their passport stamped when entering or leaving any Schengen country.
Despite this, there have been many reports of border police stamping passports leaving the British Embassy in Madrid to advise worried UK nationals who live in Spain. The embassy did say that they have been speaking to the Spanish government and have been told that border agents will receive more information about how to treat British citizens who are legal residents in Spain.
Current advice from the British Embassy in Madrid says:
You should always travel with both your valid passport and proof of your residence status, such as:
The green paper EU certificate or the new TIE or other documentation that shows you were resident in Spain before the end of the Brexit transition period.
The British Embassy stresses that even if you are resident in Spain and have had your passport stamped, it does not matter and will not affect your status. The passport stamps people have received will be considered null and void if accompanied by lawful evidence of their residence in Spain.