Starting prices

In horse racing, the starting price (SP) is the odds prevailing on a particular horse in the on-course fixed-odds betting market at the time a race begins. The method by which SPs are set for each runner varies in different countries but is generally by consensus of an appointed panel on the basis of their observations of the fluctuation in prices at the racetrack. The principal function of a starting price is to determine returns on those winning bets where fixed odds have not been taken at the time the bet was struck.

Typically, on the day of the race, UK bookmakers offer a choice between placing a bet at SP, or taking a fixed price. When viewing future races, SP may be the only option available.

Some bookmakers offer best odds guaranteed, meaning that if a punter takes fixed odds on a race when the bet is struck and the SP turns out to be better (that is, higher), then if the punter wins, the payout is calculated using the SP. This is aimed at removing hesitancy among punters prompted by fears of taking what might prove to be a poor (that is, low) price before the race.

In the United Kingdom, the stake on an SP bet is returned if the horse is withdrawn before the race starts. For fixed-odds (ante-post) bets, the stake is retained by the bookmaker.

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Wikipedia