The Pet Travel Scheme (PETS) has replaced the six month quarantine rule for both cats and dogs that enter the United Kingdom from certain countries including Australia, New Zealand, EU countries and the USA as long as they meet the rules. This scheme introduced pet passports, which act as entry documents.
The scheme allows pet owners in the United Kingdom to take their animals abroad without needing to place them into quarantine on return. Animals not covered by the pet travel scheme therefore still have to be quarantined for 6 months.
The current requirement is that pets must be microchipped, have an in-date rabies vaccination, and be given a tapewormer by a vet in the foreign country 24-120 hours (1-5 days) before returning. The rabies vaccination must be given at least 21 days before your trip.
To be properly prepared please refer to gov.uk’s “Taking your pet abroad” page.