evidence: UK passport holders are considered ‘third-country nationals’ by EU and Schengen countries. Your passport must be issued less than 10 years before your arrival date (the day you land on holiday) and be valid for three months from the final day of your holiday. [...] Some UK passports have more than 10 years of validity because until September 2018 the UK Passport Office would add any existing validity on your current passport to your new passport when you renewed. So if your old passport was still valid for nine months when you applied for a new passport, that new passport would be valid for 10 years and nine months. However, since Brexit, EU countries no longer accept the additional validity.