The association registration certificate
The core document is the registration certificate from the Rocky Mountain Horse Association. It gives the horse's registered name, foaling date, sire and dam, breeder, and the colour and markings recorded at registration. The breed is famous for the chocolate coat with a flaxen mane and tail, but registered Rocky Mountain Horses come in a range of solid colours, so what matters is that the certificate describes this horse, not the colour you expected from photographs of the breed. The seller named on the certificate should be the person you are paying. If the horse has changed hands since the certificate was last updated, those transfers need to be completed and signed off as part of the sale, not promised for later.
Registered is not the same as certified
This breed has a second status that buyers often miss. A Rocky Mountain Horse can be registered on parentage alone, but certification is a separate step in which the horse is evaluated under saddle to confirm it performs the breed's natural, even four-beat gait. The association requires certification for breeding stock, so a certified mare or stallion carries breeding value that a merely registered horse does not, and certification is noted on the horse's record. Ask the seller directly whether this horse is certified, and if so, ask to see the certification recorded rather than taking a verbal assurance. If you are buying a riding horse only, certification matters less, but it still supports the price being asked for a genuinely gaited, registered animal.
Transfer, bill of sale and the seller chain
The sale paperwork itself is straightforward: a transfer signed by the registered owner, your details as buyer, and a bill of sale identifying the horse by registered name and describing the terms of the sale, including the amount paid and any conditions agreed. File the transfer with the association straight away so the horse stands in your name. A registered breed with a relatively small population keeps close records, and a gap in the ownership chain can complicate everything from show entries to registering future foals.
Health records worth asking for in this breed
Ask for the current negative Coggins result, vaccination and deworming history, dental records and any recent vet work, plus the health certificate if the horse is travelling to you across state lines. One breed-specific request is worth adding: the silver gene behind the classic chocolate coat is associated in this breed with certain eye conditions, so past eye examination reports are genuinely useful, and asking your vet to check the eyes carefully during a prepurchase examination is a sensible step with any Rocky Mountain Horse. A seller with nothing to hide will usually be glad the records are wanted.
One packet, kept together
Registration certificate, certification record, transfer, bill of sale and health file belong together, not spread across a tack room and a glovebox. Keep scanned copies of the whole set in his KinsLe Pet Passport, and the Rocky Mountain Horse you bought arrives with his identity, his gait credentials and his health history documented in one place you can pull up whenever a vet, yard or future buyer asks.