Will your passport be valid after the transition period?
According to the House of Commons Library: “Whether or not British passport holders would be subject to third country national rules, or other rules, after the transition period, would depend on agreements on the future relationship.”
If the UK ends up leaving the EU without a deal after the transition period, rules for passports could change and you may need to take action.
In the event of a no deal exit, your passport will need to have at least six months left before it expires, and be less than 10 years old (even if it has six months or more left).
To double-check, you can use THIS tool to check whether your passport is valid for the country you’re visiting.