Most rated shows ask for a horse's USEF number. I think you can just write N/A, but I decided to get numbers for both my horses. An Annual Recording Number is $75 and a Lifetime Recording Number is $200. I wasn't interested in laying out that kind of cash, but I discovered that a horse can get a Horse ID (HID), which is surprisingly FREE!
To get your horse recorded with USEF, which gives you a number to use for rated shows, simply log on to USEF's website, find your member page, scroll down a bit, and click the bright red ADD/UPDATE button below your member info. In just minutes, you can get a USEF number for your horse.
Horses with an HID are not eligible for any awards, but you can enter breed and registry information on a profile page. And if you ever decide to pursue USEF year end awards, it's really easy to pay the fee and upgrade.
USDF offers two choices for horse registration. The first is a lot like USEF's HID except that it's not free. The Horse Identification number costs $25, but it never has to be renewed. Like USEF's HID, your horse is not eligible for any awards, but he is eligible to show. This means that while you can earn scores toward your Rider Performance Awards and Medals, scores he earns won't count for Horse Performance Certificates.
The second registration that USDF offers is a Lifetime Horse Registration (LHR). This registration costs $95, but if you went with an HID originally, you only pay $70 to upgrade (I've done this for both Speedy G and Izzy). With an LHR, your horse is eligible for all of USDF's awards and programs as long as you also hold a Participating Membership (not a Group Membership).
For more information on fees and registration types, click this link.
I joined two GMOs this year. The California Dressage Society does not charge a fee for tracking the points or scores of the horses that you ride. in fact, neither of my horses even have an ID number with CDS. I think the office keeps track of the horses simply based on their show names.
The Dressage Association of Southern California, the second GMO, does charge an annual $10 fee that allows horses to be eligible for year end awards. DASC is a tiny GMO and has so far proven to be a bit unorganized. I joined in early November and have yet to receive my membership card/number nor Speedy's number. I also just sent an application and fee for Izzy's number just in case he does make it to a rated show this year. I don't think I'll do a DASC-rated show until April, so I'll just kind of wait it out and see what happens.
Your own GMO might have a similar fee structure for registering horses. Check with them before you earn any scores.
The Grand Total
As complicated as it all seems, the bottom line is you really only need to pay a one-time fee of $25 to meet the minimum registration requirement for horses competing at USEF-licensed/USDF-recognized competitions. If you want your horse to be eligible for Horse of the Year type awards, the price goes up a little for USDF and a lot for USEF.
I'd love to hear how other GMOs deal with horse registration. Does your GMO have a fee for your horse's membership, or is it "free?"