The diseases boarders are guarding against
Boarding puts rabbits near other rabbits, and the diseases that move between them are serious ones. Services commonly require vaccination against myxomatosis and rabbit viral haemorrhagic disease — both frequently fatal, both without effective treatment once caught, and both entirely preventable. The haemorrhagic disease exists in more than one strain, and modern vaccines cover the newer variant alongside the original, so a service may check not just that your rabbit is vaccinated but that his cover includes both strains. That is the whole logic of the requirement: the boarder is protecting your rabbit from the guest in the next pen, and every other guest from yours.
What counts as proof
Expect to show the actual record, not describe it. Most services accept the vaccination card your vet stamps and signs at each appointment, or a printed summary from the practice, and many want to see it before the stay — at booking, or sent across in advance — rather than at the door with a car full of luggage. Some note the details on the booking and check the card again at drop-off. If your rabbit's records live across two practices because you have moved, gather both parts ahead of time; a gap in the paperwork will be treated as a gap in cover, whatever the truth of it.
How far ahead to arrange it
If your rabbit's vaccinations are simply current on their annual cycle, you have nothing special to arrange beyond locating the proof. The forward planning matters when he is unvaccinated, lapsed, or a young rabbit who has not had a first course: book the vet appointment weeks before the boarding stay, not days. A newly vaccinated rabbit needs time for protection to build before he is sitting in a room full of other rabbits, and a first appointment can also surface the question of whether a second visit is needed to complete cover. Vets also get busy in holiday seasons — precisely when boarding is booked — so the appointment that is easy to get six weeks out may not exist six days out.
Questions worth asking the service
Ask at booking, in plain terms: which vaccinations do you require, do you need cover against both haemorrhagic strains, how do you want to see the proof, and is there a minimum time you want between vaccination and arrival? Services differ — a small home boarder and a large facility may run slightly different rules — and the only version that matters is the one belonging to the service you are using. Ask also what else they require, since some ask about flea treatment or a recent health check in the same conversation.
Keeping the proof where you can find it
The recurring failure in all of this is not an unvaccinated rabbit; it is a vaccinated rabbit whose card is in an unknown drawer the night before drop-off. Storing the record in his KinsLe Pet Passport, alongside the rest of his health paperwork, means the proof a boarder asks for is in the same packet every time — ready to show at booking, ready again at the door, and ready for the vet visit where the next booster is recorded.