Requote loops and the deviation setting

[Shadow Trader]

Some platforms ask for a maximum deviation, the number of points by which the fill price may differ from the requested price. The setting looks minor and controls a lot.

A deviation of zero demands the exact price. In fast markets, price moves between click and execution, so zero deviation produces frequent rejections or requote messages. Each requote means another attempt at a worse price, and loops can develop where the trader chases a moving market.

A generous deviation, say 30 points, almost guarantees fills, but permits poor prices. For a scalper with a 4 pip target, a 3 pip deviation is enormous.

The right value balances fill rate and price quality. A practical approach logs outcomes for a few weeks at a given setting, noting the rejection rate and the average slippage. Adjusting in small steps shows where the sweet spot lies.

Different instruments and sessions justify different values. Spreads and volatility around news call for wider tolerance, calm periods for narrower.

Some brokers ignore the deviation field entirely and use their own execution rules. Testing reveals whether the setting has any effect.

A sample trial: run a week with a deviation of 3 points, a week with 10, a week with 20, using small size and the same entries. Compare rejection counts and average slippage. The comparison often shows a sharp improvement in fills between 3 and 10, then little extra benefit from 10 to 20 beyond worse average prices.

What deviation setting works, and does it vary between sessions?