Additional months of validity on UK passports issued before the UK left the EU are no longer valid.
Passports are now only valid for 10 years exactly - additional months on anyone's red passports (passports issued before the UK left the EU ) are no longer valid. [...] A statement from Hays Travel said: "Important passport update changes: due to changes in validity since leaving Europe, your passport is now only valid for 10 years from the issue date on your passport. "If your passport was issued prior to the UK leaving the EU with additional months on, those extra months are no longer valid."