Betfair SP (Starting Price) Explained

What Is Betfair SP?

Betfair Starting Price (BSP) is a computer-generated price calculated at the moment a horse race starts (or turns in-play). Unlike manually placing a bet at a specific price, BSP bets are matched at whatever price Betfair's algorithm generates at the start — you don't control the exact price you receive.

BSP is available on UK and Irish horse racing Win markets and a small number of other race types. It is not available on football, tennis, cricket, or most other sports.

The key purpose of BSP: it allows you to get matched on a race without being present at your screen at the moment the race starts. If you want to back or lay a horse but can't watch the market closely in the final minutes, you queue a BSP bet and accept whatever price the algorithm generates at the off.

How BSP Is Calculated

Betfair's BSP algorithm works by collecting all BSP back orders and BSP lay orders that have been placed before the market turns in-play, then finding the price at which the maximum amount of money can be matched. The process at race start:

1. The market turns in-play and regular betting is halted briefly
2. All unmatched regular orders that have "keep" instructions are processed
3. BSP back and lay orders are collected by the matching engine
4. The algorithm calculates the single price that balances maximum matching across all BSP orders — similar to a call auction in financial markets
5. All BSP orders are matched at this single price, and the market opens for in-play trading

Crucially, regular pre-race orders also influence BSP. If there's heavy unmatched back money at 4.00 at race start, it will be matched against BSP lay orders, pulling the BSP price downward. BSP is not independent of the pre-race market — it's the equilibrium that resolves all remaining pre-race liquidity at the start moment.

BSP vs Traditional SP

Traditional SP (Starting Price) in UK horse racing is calculated separately from Betfair and is set by the racecourse offices based on on-course bookmaker prices. Betfair BSP and traditional SP are independent calculations that often differ — sometimes significantly.

BSP typically runs close to the final traded Exchange price — usually within 5–10%. Traditional SP can diverge more significantly from Exchange prices, especially on shorter-priced runners where the racecourse SP may lag behind heavy Exchange market movements.

Traditional bookmakers quote "industry SP" which derives from the racecourse offices. When a traditional bookmaker says "best odds guaranteed at SP", they're comparing to traditional SP, not Betfair BSP. These are different numbers for the same race.

For matched betting: some bookmaker offers state "back at SP" — this means traditional industry SP, not Betfair BSP. Know which SP you're comparing against.

How to Place a BSP Bet

On the standard Betfair website:

1. Navigate to the horse racing Win market
2. Click "SP" next to any selection in the back or lay column (the SP button appears alongside the regular price buttons)
3. A bet slip opens showing "SP" as the price — you cannot enter a specific price
4. Enter your stake (for a back bet) or backer's stake (for a lay)
5. Confirm the bet — it sits in your unmatched bets as "BSP" until the race starts, then settles at whatever BSP is calculated

You can place BSP bets right up until the market is suspended (typically 5–30 seconds before the off depending on race type). You can cancel a BSP bet before the market is suspended.

When Should You Use BSP?

BSP makes sense in specific situations:

• You can't be at your screen at race time. If you want to back a horse in the 3:15 but you'll be in a meeting, placing a BSP back bet guarantees you're matched at a fair market price without manual intervention.
• You're running automated systems across many races. Bots and systematic bettors often use BSP to scale across high volumes of races without managing each one individually.
• You have unmatched orders you want resolved at the off. You can set unmatched pre-race orders to convert to BSP at race start rather than being cancelled.
• Liquidity is thin on the selection you want. On unpopular horses in small fields, BSP guarantees a fill even if there's insufficient regular liquidity at your target price.

BSP is generally NOT the right choice when:

• You have a specific price target in mind — BSP may give you worse than your target
• You're trading — BSP locks you in at race start with no ability to manage the position pre-race
• The horse is heavily backed pre-race — BSP may be significantly shorter than the available pre-race price if there's a steam

Unmatched Bets and BSP at Race Start

When a horse racing market turns in-play, all remaining unmatched bets have one of three fates, depending on the order instructions you set when placing:

1. "In-Play" enabled: The unmatched order carries over into in-play and can be matched post-race start at your requested price (if liquidity allows)
2. "Match at BSP": The unmatched portion is converted to a BSP order and matched at the BSP price
3. Cancel at race start: Unmatched order is automatically cancelled at the off

By default on the Betfair website, unmatched bets are typically cancelled at the off. Trading software allows you to configure this behaviour. Most active traders cancel unmatched orders at the off — carrying unmatched pre-race positions into in-play is a separate, often riskier activity.

How Traders Use BSP

Most active pre-race traders have no use for BSP in their normal workflow — they're focused on getting specific prices and controlling their entry and exit precisely. BSP removes that control.

Where BSP is used by more sophisticated traders and system operators:

• Systematic backing at BSP: Some quantitative traders have models that identify horses they believe are undervalued at BSP (relative to true probability). They back at BSP across many races, expecting their model's edge to compound over large sample sizes. BSP is the only way to execute this at scale.
• BSP lay systems: Similarly, systematic layers who identify overvalued runners use BSP lay bets. The risk is higher because BSP lay prices are less predictable — but the convenience of guaranteed matching is valuable at volume.
• Cleaning up pre-race trades: If a pre-race trade position isn't fully greened up by race start (some unmatched hedge orders remaining), converting the residual to BSP can be used as a final exit mechanism. This is a last resort — the BSP price may not be favourable.

For any trading strategy that requires specific price control, manual market betting is superior to BSP. For volume-based systems where guaranteed matching is worth accepting an unknown price, BSP is the right tool. See What Is Betfair Trading? and Horse Racing Trading Guide for how most traders approach pre-race markets.