Since January 1st 2016, Flat Races have been classified as highlighted below. In some races, some horses may be asked to carry penalties for winning higher-class races, whilst in handicaps horses carry weights according to their official ratings. Meanwhile, in races with the suffixes Apprentice or Amateur all horses will be ridden by those types of jockeys.
Class 1 Races
Group 1: Generally won by horses rated 125 and higher, with minimum prize-money of £150,000
Group 2: Generally won by horses rated 115 to 124 with minimum prize-money of £65,000
Group 3: Generally won by horses rated 110 to 115, with minimum prize money of £40,000
Listed Races: Usually won by horses rated 100 to 109
Class 2 to Class 7 Races (Class is dictated by ratings)
Heritage Handicaps: Handicaps often contested by horse of Group or Listed Standard with a minimum of £100,000 Prize Money
0-105 or 0-110 Handicaps: Open handicaps with prize money of at least £45,000
Conditions Stakes – Contested by horses rated up to 100
Limited Handicaps: Only horses rated between the specified ratings can compete e.g. 86-100
Nursery Handicaps – Open handicaps that are only contested by 2-year-olds
Classified Stakes: Contested by horses rated between 0-95
Maiden: Contested by horses who have never won before
Novice: Races for 2-year-olds who haven't won more than 2 races (also can't have won a class 1 or more than one class 2 or class 3 race.
Novice Auction Race: As above, but for horses that were bought at public auction
Median Auction Race: As above, but only for the offspring of certain stallions who fetch an agreed median price at auction
Claimer: All horses in the race may be claimed by a third party for the claiming fee, with the size of the claiming fee dictating how much weight a horse must carry during the race
Seller: Similar to a claimer, but the winner is auctioned off afterwards in the ring if anyone wants to buy it.
UK National Hunt Chases, Hurdle Races & Flat Races (Bumpers)
Grade 1: Reserved for the best Chases, Hurdles and Bumpers, such as many of the races run at the Cheltenham and Aintree Festivals
Grade 2: Reserved for many of the races that are viewed as trials for the Grade 1 Races
Grade 3: Often contested by horses who are rated just below Grade 1 and Grade 2 standard
Listed Races: Often used as a stepping stone for handicappers who have Graded Race winning aspirations
Open Handicaps: Available to all horses that have been allocated an official rating by the British Horse Racing Authority
Weight-for-age Conditions Races: Horses are asked to carry weights according to their age rather than their official rating
Novice Chases/Hurdles: Open to horse who have not won a race in their chosen discipline before the current season began
Open Novices' Handicaps: Handicaps for which only novice chases or hurdlers are eligible
National Hunt Flat Races: Flat races for National Hunt horses that have not participated in a flat race under flat racing rules
Hunter Chases: The Hunter Chase Season runs from January 1, and is open to horses who haven't run a chase under National Hunt Rules within the qualifying period
*National Hunt Racing also operates a structure that includes varying classes of racing which are designed to allow horses to race against other horses of similar ability, and these classes are class 1 to class 6.