Most races are governed by organizations such as NORBA (National Off-Road Bicycling Association) and USA Cycling. To enter these races you're required to purchase a racing license. Depending on the event, you might be able to buy a one-day license. However, if you plan to race regularly, you should probably purchase a regular license, which will cost more, but will permit you to race all year long. There are also races that aren’t sanctioned and may or may not require a license. Whatever the type of race, always register early to avoid paying late fees and to avoid the long registration lines the day of the race.