Positive slippage exists, but does the broker pass it along?
Posted: Sat Oct 31, 2026 8:20 am
Everyone talks about negative slippage. Positive slippage, where the fill lands better than the requested price, gets less attention, and it shows how a broker really handles orders.
On a symmetrical execution model, slippage is roughly as likely to help as to hurt. Over a few hundred trades, the average should be close to zero, with a fat tail on both sides. Prices move in both directions between click and fill, and an honest pipeline passes along whichever one happens.
Some brokers don't behave that way. The tally shows far more negative slippage than positive, or positive fills get capped, or price improvement is quietly kept by the broker. That's called asymmetric slippage, and it adds up to real money on a scalping account.
The test is simple. Export the trade history, calculate requested versus filled price on every market order, and sort the results into better, equal and worse. Even a basic spreadsheet makes the pattern obvious.
A few ways the asymmetry can show up:
- Positive slippage appears, but only up to a small cap, while negative slippage has no cap
- Positive fills arrive later than negative ones, giving price time to move back
- Orders that would have improved are rejected and re-quoted at the original level
- The share of exact fills at the requested price is unusually high
Some caveats keep the test honest. Pending orders and market orders slip differently, and news periods skew the numbers. Separating those out before drawing conclusions avoids false alarms. A sample of at least a few hundred trades is needed, since small samples are noisy.
Anyone who has run this test and found a lopsided result already has an answer about the broker. A symmetrical result is good news worth having in writing.
What did the slippage distribution look like on a real account, and did it change the choice of broker?
On a symmetrical execution model, slippage is roughly as likely to help as to hurt. Over a few hundred trades, the average should be close to zero, with a fat tail on both sides. Prices move in both directions between click and fill, and an honest pipeline passes along whichever one happens.
Some brokers don't behave that way. The tally shows far more negative slippage than positive, or positive fills get capped, or price improvement is quietly kept by the broker. That's called asymmetric slippage, and it adds up to real money on a scalping account.
The test is simple. Export the trade history, calculate requested versus filled price on every market order, and sort the results into better, equal and worse. Even a basic spreadsheet makes the pattern obvious.
A few ways the asymmetry can show up:
- Positive slippage appears, but only up to a small cap, while negative slippage has no cap
- Positive fills arrive later than negative ones, giving price time to move back
- Orders that would have improved are rejected and re-quoted at the original level
- The share of exact fills at the requested price is unusually high
Some caveats keep the test honest. Pending orders and market orders slip differently, and news periods skew the numbers. Separating those out before drawing conclusions avoids false alarms. A sample of at least a few hundred trades is needed, since small samples are noisy.
Anyone who has run this test and found a lopsided result already has an answer about the broker. A symmetrical result is good news worth having in writing.
What did the slippage distribution look like on a real account, and did it change the choice of broker?