Britons wanting to take their pets to Northern Ireland or abroad to the EU next year will have to apply for an animal health certificate under new post-Brexit rules.
However, more stringent checks will not be needed following an agreement with Brussels, the UK government announced on Wednesday.
Until the end of the Brexit transition period on 31 December, Britons will continue to be able to take their cats, dogs and ferrets to EU countries with them - and return to the UK again - if the usual conditions are met.
These include having a pet passport, having your pet microchipped and having your pet vaccinated against rabies.
However, from 1 January, pet passports will no longer be valid for trips to either the EU or Northern Ireland and those travelling with their cats, dogs or ferrets will have to use an animal health certificate instead.
The government says this is the only new requirement for post-Brexit travel to the EU with pets or assistance dogs, after the UK was granted Part 2 listed status by the European Commission under the bloc's pet travel scheme.
The full requirements for taking pets to the EU or Northern Ireland for the first time after 1 January are:
You must have your dog, cat or ferret microchipped
Vaccinate your dog, cat or ferret against rabies - your pet must be at least 12 weeks old before it can be vaccinated
Wait 21 days after the primary vaccination before travel
Treat your dog against tapeworm 24-120 hours before arriving, if you are travelling to a tapeworm-free country
Visit your vet to get an animal health certificate for your pet, no more than 10 days before travel to the EU.
An animal health certificate needs to be signed by a vet after they have been given proof of a pet's microchipping date and vaccination history.
The certificate will be valid for 10 days after the date of issue for entry into the EU or Northern Ireland, onward travel within the EU or Northern Ireland for four months after the date of issue, and re-entry to Great Britain for four months after the date of issue.
Pets and assistance dogs will also need to enter the EU through a travellers' point of entry, which includes all the major French ports such as Calais, Caen and Dunkirk.
If the UK had been denied listed status by the EU, pet owners could have faced further requirements such as needing a pet's blood sample to be sent to an EU-approved testing laboratory.
The government said it would continue to press the EU to be granted Part 1 listed status, which would mean the requirements for pet travel for Britons could remain very similar to as they are before 31 December.
The Department for Environment, Food and Rural Affairs said the UK "has one of the most rigorous pet checking regimes in Europe and currently meets all the requirements for Part 1 listed status".
It added that there will be no change to the current health preparations or documents for pets entering Great Britain from the EU or Northern Ireland from 1 January.
Christine Middlemiss, the UK's chief veterinary officer, said: "We have been granted Part 2 listed third country status by the EU which will ensure that travelling with your pet continues from 1 January onwards.
"Your vet will be able to advise what you need to do in order to obtain the correct documentation to travel and you can find the latest pet travel advice on gov.uk or by searching 'pet travel'."
The government said it was working with the Northern Ireland Executive to agree an approach to enforcing the new requirements that "supports pet owners and assistance dog users while the government pursues a permanent solution".