https://www.gov.uk/foreign-travel-advic … quirements
At Spanish border control, you may need to use separate lanes from EU, EEA and Swiss citizens when queuing. Your passport may be stamped on entry and exit. You may also need to:
o show a return or onward ticket
o show you have enough money for your stay
o show proof of accommodation for your stay, for example, a hotel booking confirmation, proof of address if visiting your own property (e.g. second home), or an invitation from your host or proof of their address if staying with a third party, friends or family. The Spanish Government has clarified that the “carta de invitation €74” is one of the options available to prove that you have accommodation if staying with friends or family. More information is available from the Spanish Ministry of Interior.