Border Force and the Animal and Plant Health Agency (APHA) check pet travel documents at GB ports and airports, and a pet that doesn't meet the requirements — a missing microchip match, an AHC issued outside its window, a tapeworm treatment given too early or too late — is treated as non-compliant. The realistic outcomes range from a hold-up while paperwork is sorted on the spot, to the pet being refused entry entirely, to quarantine arranged at the owner's own cost.
The most common real-world trigger isn't fraud or a genuinely sick animal — it's timing. An AHC issued 12 days before travel instead of 10, or a tapeworm treatment given 6 days before arrival instead of within the 5-day window, is enough to fail the check, even though the underlying treatment itself was perfectly valid.
If something has gone wrong before you travel — a missed appointment, an illness that delayed the rabies vaccine — it's worth contacting APHA's pet travel line directly rather than hoping a border check won't notice. APHA can advise on next steps, and sorting it out before you travel is always a better position than discovering the problem at the port.