The paper move is not the executed result
| Record | Why it is needed |
|---|---|
| Best back and lay with size | Shows the spread and immediately available liquidity |
| Request timestamp | Places the instruction in the event and market sequence |
| Matched parcels | Reconstructs weighted execution rather than intended price |
| Unmatched remainder | Identifies residual or cancelled instructions |
| Market status | Excludes fills assumed during suspension |
| Open liability | Measures the position while only one side is matched |
| Commission basis | Converts gross market settlement to net cash result |
Betfair's exchange rules explain matching, price-time priority, cross-matching and market administration for that exchange. A requested order has no offsetting effect until it is matched.
Illustrative equalisation
Suppose GBP 100 is backed at 2.20 and a lay later becomes fully available at 2.18.
Equalising lay stake = (2.20 * GBP 100) / 2.18 = GBP 100.92
Before commission and rounding, the combined result is approximately GBP 0.92 whether the selection wins or loses. That small gross amount can be reduced or removed by worse execution, unmatched size or commission. The example demonstrates arithmetic only; it is not an attainable-return claim.
Model the queue and spread
Historical last-traded prices do not show that a new request would have filled. The Betfair historical feed specification documents available ladders, traded volume, publish times and status, but a backtest still needs a conservative queue and fill rule. Report sensitivity to no fill, partial fill and one-tick adverse movement.
Use the exchange trading guide for the underlying back, lay, matching, liability and commission contract before evaluating a short-horizon method.
Treat suspension as exposure
A material football event can suspend the market while one side of a planned pair remains open. The Gambling Commission's in-play standard warns that live information may be delayed. A simulation that assumes instantaneous event data and uninterrupted matching understates operational risk.
Net result and validation
Betfair's commission guidance describes commission on net market winnings for its exchange. Store gross result, applicable rate and net cash separately, then evaluate all eligible signals, including no fills and unfinished offsets.
A defensible chronological test should specify:
- market and competition universe;
- data and price timestamps;
- entry side, price and queue rule;
- exit rule and maximum holding interval;
- suspension and unmatched-order treatment;
- liability and concurrent-position cap;
- commission and rounding;
- later-period evaluation with every attempted instruction.
Failure conditions
Stop the method when clocks cannot be aligned, available size is absent, fill assumptions cannot be reproduced, event corrections are missing, or one-sided exposure exceeds the preset bound. Do not infer skill from a small number of completed round trips.
Continue learning
- Next guide: Goals After a Goal
- Related guide: Half-Time In-Play Analysis
Assumptions and limitations
The example assumes full matching at two prices and omits tick-size constraints and commission from the displayed gross result. Real queue position cannot always be reconstructed from public data. Short holding periods do not remove market, information, execution or gambling-harm risk.
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