The British Ambassador in Madrid is advising  all UK nationals in Spain with green EU residence cards  who will travel abroad in the future to obtain a TIE card

This is to avoid problems at passport control with the new Entry Exit System ( EES) coming into use in Autumn 2025.

This is a summary of the information from the ambassador: “This month, the European Union (EU) has published draft legislation in preparation for the EES coming into force in Autumn 2025. It states that Green Certificates will not be recognised by the EES, in Spain or any other Schengen country. It has now been made clear  that Green Certificate holders travelling in and out of Spain should expect difficulties, which could range from lengthy delays, to being denied entry, to possibly being banned from the Schengen area. There remains time for British residents to get a TIE if they act now.  https://www.gov.uk/guidance/living-in-spain#visas-and-residency . We understand that there are now enough appointments available in key areas.”