A horse's passport is its legal identity document, but a document only protects you if the horse standing in front of you is the horse described in it. Age and breeding are the two claims sellers most often get wrong — sometimes innocently, sometimes not — and both can be checked: the age against the horse's teeth, and the breeding against registry records and, where it matters, DNA. Work through the document first, then the mouth, then the registry, and treat any mismatch between the three as a warning.
Make the passport match the horse
Open the identity section and compare it line by line with the animal: colour, sex, height, and the markings and whorls, which are drawn or described precisely because they are hard to fake. A passport describing a blaze and two white socks should not be standing in front of you on a plain-faced horse with four dark legs. Then check the microchip. Every passport carries a chip number; a vet with a scanner can read the chip in the horse's neck and confirm the numbers agree. No chip found, or a number that differs, means the passport belongs to another horse and every claim attached to it — age, breeding, vaccination history — is worthless for this animal.
What the passport says about breeding
The breeding section records the horse's sire and dam and its breed society registration, and for a horse sold as well-bred this is the paper trail that supports the price. Check that the registration number is genuine by contacting the breed society, which can confirm the horse is recorded as described and that the recorded ancestry in the passport matches its register. Where a lot of money or a future breeding career depends on parentage, societies can verify it directly: DNA taken from hair roots can be compared against the recorded sire and dam. That level of proof is overkill for a happy hacker, but for a breeding prospect or a competition horse it converts a seller's story into a fact. Note what a passport is not: it proves identity and recorded breeding, not ownership, so it should travel with the horse while the bill of sale proves the horse is yours.
Reading age from the teeth
Teeth give an estimate independent of any paperwork, and a vet or experienced horse person reads them from the incisors. Young horses are aged by which teeth have erupted; adults are aged by wear. The cups — the hollows in the centre of the chewing surface — wear away from the lower incisors in a predictable sequence through roughly the first decade, while a smoother, triangular surface and a steeper angle between upper and lower teeth mark the older horse. The best-known marker is Galvayne's groove, a line that appears on the surface of the upper corner incisor at around ten years of age, extends about halfway down the tooth by the mid-teens, reaches the bottom at around twenty, and then disappears from the top down through the twenties. Teeth give a range, not a birthday — diet and habits like crib-biting wear them unevenly — but they are good at exposing a horse sold as eight who is nearer fifteen.
Putting the three checks together
The honest horse passes all three: passport markings and chip match the animal, the registry confirms the breeding, and the teeth sit inside the claimed age. A one or two year difference between teeth and passport in an older horse is normal error and no scandal. A different picture — young papers on old teeth, markings that do not match, a chip that does not scan — is the point to walk away, because a seller who is wrong about the verifiable things is unlikely to be right about soundness or temperament. Once the checks pass and the horse is yours, keep the evidence together rather than in a glovebox and a drawer: KinsLe's Pet Passport holds the horse's records in one portable packet, so the identity, breeding, and vet findings you verified are ready for every vet visit, journey, and yard move that follows.