When showing in the hunter jumper ring the hunter judge will score you a major error if your horse refuses. There are many different types of errors that are considered disobediences and marked as major errors.
Major Errors Include:
A horse is considered to have refused when it stops in front of an obstacle, without jumping it. Please note that if your horse steps back, even just one step, whether the rider asked the horse to go back or not, it is considered a refusal.
A horse is considered to have ‘run out’ when the horse, or any part of the horse, goes past the extended line of the obstacle. This can be seen in novice classes where clever school horses have perfected the art of veering past the fence with a bulging shoulder.
Resistance/stopping on course
A resistance is a catch-all phrase to encompass other displays of disobediences that can occur on course. This can include a horse stopping on course, for any reason, halting, rearing, stepping back or other displays. If your horse stops on course, for any reason it will be counted as a disobedience and scored as such.
It is permissible to make a courtesy circle at the beginning of your round and also to complete your round with a finishing circle. Any other circles on course will be counted as a disobedience.
Discussion on Disobediences