Additional months of validity on UK passports issued before the UK left the EU are no longer valid.
Booking a holiday to beat the January blues? You better check your passport. When the Brexit transition period ends, Brits will need a minimum of six months left on their passports to travel to Schengen Area countries, which applies to most of Europe. [...] To make things more complicated, if you renewed your current passport before the previous one expired, any remaining validity (up to nine months) would likely have been added to its expiry date over the usual limit of 10 years. However, any extra months on your passport may not count towards the six months required. This is because Schengen Area countries also require passports to have been issued within the last 10 years on the day of travel. [...] Yes. British passports will continue to be valid until their expiry date for entry to the UK. The rule changes resulting from the end of the transition period only apply for entry to a state where the Schengen Borders Code is applicable.