Microchip before anything else
The chip must be an ISO 11784 and 11785 compliant transponder, implanted and scanned before the rabies vaccination is given. A vaccination administered before the chip does not count for British entry whatever the record says, and the sequence has to start again. Ask for the number to be scanned and read out at the appointment, then check it digit by digit against every document that follows, because one wrong digit is a standard reason a dog is held at the border. A dog carrying an older non-ISO chip can have a second compliant chip implanted, with both numbers recorded on the paperwork from that point on.
Rabies vaccination and the 21 days
After the microchip, the dog needs a rabies vaccination given by a vet at 12 weeks of age or older. You then wait at least 21 full days from the date the vaccination was completed before the dog may enter Great Britain, counting the day of vaccination as day zero. A dog travelling from a country outside the recognised parts of the scheme also needs a rabies antibody blood test drawn at least 30 days after vaccination, followed by a three-month wait before entry. Boosters have to stay in date without a gap: one late dose resets the 21-day clock and, where it applies, the blood test as well.
The Great Britain health certificate
A dog arriving from the EU or Northern Ireland can travel on a valid EU Pet Passport. Everyone else needs a Great Britain pet health certificate, completed by an official vet in the country of departure and issued within ten days of the arrival date. It names the owner, describes the animal, records the microchip number and implant date and restates the rabies dates, so any mismatch with the vaccination record is easy to spot. Certificates issued outside the EU usually also need endorsement by the exporting country's government animal-health authority after the vet signs, which takes days rather than hours. Once used, it covers onward EU travel for four months and the return within that window.
Tapeworm treatment before arrival
Dogs entering Great Britain need treatment against Echinococcus multilocularis, given by a vet no less than 24 hours and no more than 120 hours before the scheduled arrival time. The vet records the product name, the manufacturer, and the date and time of treatment, then signs the entry in the passport or certificate. The window is the strict part: a dose given 20 hours or 130 hours out is invalid, and a delayed ferry or a missed connection can push arrival past the limit. Dogs coming directly from Ireland, Northern Ireland, Finland, Malta or Norway are exempt. Cats and ferrets do not need the treatment at all.
Approved routes and arrival checks
A pet may only enter Great Britain on an approved route with a carrier authorised for that journey — named airlines, ferry operators and Eurotunnel services. Dogs cannot arrive in the aircraft cabin as ordinary passengers' pets; they travel as checked baggage or as manifest cargo, with registered assistance dogs the main exception. The carrier checks documents and scans the microchip before departure, and a further check follows on arrival, so allow time at both ends. Where something is wrong, the dog is placed in quarantine at the owner's expense until it is corrected, which for a missed 21-day wait means the full period. No more than five dogs may travel per person on non-commercial rules.