For travel from the UK to Spain in 2026, the most critical new requirement is the ETIAS (European Travel Information and Authorisation System). This is a mandatory electronic authorization linked to your passport that must be applied for online at least 96 hours before departure. Additionally, you need a valid British passport that was issued less than 10 years ago and is valid for at least three months beyond your planned date of departure from Spain. Since the UK is a "third country" in 2026, you may also be asked for proof of accommodation (hotel booking), a return or onward ticket, and evidence of sufficient funds for your stay (approximately €113 per person per day). While a visa is not required for stays under 90 days, you should also carry your GHIC (Global Health Insurance Card) or a valid EHIC to access state healthcare. Border officials in Spain are increasingly strict about checking these documents at major airports like Madrid and Barcelona.