Instructions
Select which association you want to register your horse with. See the resources section for a list of respectable breed associations that will accept virtually any horse into the registry. If your horse has a specific color characteristic, you may be able to register it with a color-based registry (Palomino, Pinto) as well.
Fill out the registration paperwork. You will need to go through virtually all the same steps that you would if you were registering a purebred horse, except that grade horse registries will allow you to answer "unknown" to the horse's breed or pedigree. Remember to select a unique registered name for your horse.
Send in the breed registry paperwork along with all required fees. If you plan on breeding the horse, you may have to submit several strands of your horse's mane or tail for DNA typing. DNA typing is done so that offspring of your horse can have their lineage verified when they are registered. If you are not a member of the registry, be prepared to pay fees to join it. If the registry you choose requires a horse inspection, schedule the inspection and allow your horse to be evaluated.
Wait for registration papers to arrive in the mail. When they arrive, your horse has been officially registered. Store papers in a safe location.
How to Register Crossbreeds of Unknown Lineage
Registering a crossbred horse of unknown lineage is challenging because the horse will not meet most of the requirements currently presented by horse breed associations in order to allow registration. Fortunately for the owners of these horses as well as horses that should be registrable but lack the proper paperwork or have unacceptable markings or colors, there are several breed registries that will accept any horse, of any lineage, age, size, color or breed to be registered with their registries. These registries exist to allow grade horse owners to document their horse's and provide a paper ownership trail for such animals.