Some pet passports become invalid today due to new EU travel rules.
Anyone travelling to one of the bloc's member states with dogs, cats and ferrets will now need to get an animal health certificate before they set off.
It will need to be issued by a vet within 10 days of their trip, and a new one will be needed for every future journey from Britain into the EU.
It can, however, be used for up to six months for onwards travel within the EU and for re-entering Britain.
A message on the UK government website states: "If you live in England, Scotland or Wales, from 22 April you cannot use a pet passport (even if it was issued in the EU).
"If you use a pet passport, your pet may be refused entry into the EU."
The rules also apply to assistance dogs.
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Other new rules include a limit of five pets in a single private vehicle and for owners to provide written permission for their animal to travel with someone else.
EU pet passports are now only being issued to people whose main base is in the EU and not to seasonal visitors or holiday home owners.
The government said they would still be accepted for British-based travellers returning home.
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