To be exempt from registering with the EU’s Entry Exit Scheme (the exact date that EES will be introduced has not been confirmed) British residents in Spain will be required to show a TIE.
This is the only residency document listed in the EU Schengen Border Guard Handbook and therefore, the only document which border offices will accept as legal proof of residency.
GREEN CERTIFICATEDS WILL NOT BE RECOGNISED and Green Certificate holders may be wrongly identified as overstaying in the Schengen area and therefore, denied entry to Spain or other Schengen countries. Contact the Spanish Government’s ‘Extranjeria’ offices for information on how to apply for the new TIE.
https://www.policia.es/…/dependencias_localizador…#