A trader works out exactly how much room the daily loss limit leaves, places a stop at the level that keeps a losing trade inside it, and goes to make coffee. A data release prints, the stop triggers, and the fill comes back well past the level on the chart. The trade closed where it was supposed to. The account did not. A loss sized to leave a margin of safety has arrived as a breach, and nothing about the plan was wrong.
That gap between the expected price and the price actually received is slippage, and it is a property of markets rather than a fault in them. Foreign exchange is the deepest market in the world, with daily turnover reaching $9.6 trillion in April 2025 according to the Bank for International Settlements, and slippage happens there too. Depth is never spread evenly across the day, and it disappears fastest at exactly the moments traders most want to act.
What Slippage Actually Is
An order is a request to trade at a price. Between the moment it is sent and the moment it is filled, two things can happen: the market can move, or the size quoted at that price can be taken by someone else. Either way, the order fills at the next price available, which may be better or worse than the one requested.
It runs in both directions, which is the part traders forget. Positive slippage, where the fill comes back better than expected, is common in fast markets moving in the trader’s favor. It simply gets noticed less, because nobody studies a trade that went slightly better than planned.
Slippage is also not the spread. The spread is the known cost of crossing between the bid and the offer, visible before the order is placed. Slippage is the deviation from what was expected once the order goes in, which makes it the harder one to plan around.
When It Shows Up
Slippage concentrates in predictable conditions, which is what makes it manageable rather than random.
| When It Happens | What Is Going On | What a Trader Sees |
| Scheduled news releases | Quotes widen and depth thins out for a few seconds | Fills several points away from the trigger price |
| Session opens and closes | Price reprices against news from the hours the market was shut | Gaps straight through a stop level |
| Thin hours | Fewer participants quoting, so less size at each price | Worse fills on an otherwise quiet chart |
| Size against available depth | The order consumes more than is quoted at the first price | An average fill worse than the price clicked |
| Weekend crypto trading | Lower participation while other markets are closed | Sharper moves and wider gaps than on a weekday |
Why It Matters More Inside an Evaluation
In a personal account, slippage is a cost. It makes a good year slightly less good and a bad month slightly worse. In an evaluation, it meets hard thresholds, and a threshold does not care whether the trader intended to cross it.
Stops and Daily Boundary
A trader who sizes a loss to land just inside the daily limit has built no tolerance for a worse fill. The same trade with a few points of slippage lands just outside it. Treating the published limit as the target rather than the ceiling is the single most common way an otherwise sound plan ends an evaluation.
Size and Leverage
Slippage scales with position size, because a larger order works through more of the available depth before it is filled. Available leverage makes this easy to underestimate: a size that feels reasonable against account equity can be large against what is quoted at a given price in a thin hour. The fill reflects the second number, not the first.
Trailing and Maximum Drawdown
Where an account uses a trailing drawdown, a worse fill does more than cost money once. It lowers the balance the trailing figure is measured from, so the floor moves up to meet the trader and the room available for the rest of the evaluation shrinks. A single bad fill on a volatile morning can tighten the account for days afterward, which is why traders running these accounts tend to be more careful about when they trade than about what they trade.
Strategies Most Exposed
Approaches built on many small wins feel it most, since a point or two lost on each entry and exit removes a large share of a thin margin. Trading the first seconds of a scheduled release is the clearest case of all, because that is precisely when depth is thinnest and quotes move fastest.
What Traders Can Do About It
Slippage cannot be removed, but most of the damage it does inside an evaluation is avoidable.
- Leave a buffer between the planned loss and the daily limit rather than trading to the edge of it.
- Size against the depth available at the time of day being traded, not against account equity alone.
- Know the release calendar for the instrument, and decide in advance whether to be in a position through it.
- Use limit orders where the approach allows, accepting that the trade-off is an order that may not fill at all.
The release calendar point does most of the work. A trader who knows when the scheduled events are can decide whether to hold through them deliberately, rather than discovering the answer from a fill.
It is also worth knowing how the instrument itself behaves. Major currency pairs in London or New York hours are about as forgiving as markets get. Index and energy futures tend to move hardest around their own opens and around inventory or policy releases. Crypto has no session structure to work around, so the thin periods arrive whenever participation drops rather than at a published time. A strategy carried from one of these to another without adjusting for that difference usually finds out through its fills.
What Firms Should Make Clear
Slippage generates more support tickets than almost anything else, and nearly all of them come from the same place: a trader who did not know what to expect. The firms that handle it best publish the mechanics plainly, including which price a rule is assessed against, that slippage runs in both directions, and what the account data shows after an unexpected fill.
That clarity is a product decision before it is a support one, and it depends on the account data being detailed enough to answer the question when a trader asks it. Operators building on PropAccount.com can show the fill behind a rule outcome rather than only the outcome, which turns an argument about what happened into a conversation about what the market did.
Frequently Asked Questions
Q: What is slippage in trading?
The difference between the price a trader expects when placing an order and the price the order actually fills at. It happens when the market moves between the order being sent and executed, or when the size available at the expected price runs out.
Q: Is slippage always bad?
No. It runs in both directions. Positive slippage, where the fill is better than expected, happens regularly in fast markets, though traders tend to notice only the fills that went against them.
Q: What causes slippage in prop firm accounts?
The same conditions as anywhere else: scheduled news releases, session opens and closes, thin trading hours, orders large relative to available depth, and instruments that trade through periods of low participation.
Q: Can slippage cause you to fail a challenge?
It can contribute. A stop placed so that the loss lands just inside a daily limit leaves no room for a worse fill, which is why traders are generally advised to plan against a buffer rather than the exact published figure.
Q: How can traders reduce slippage?
Trade in hours with more participation, size positions against available depth rather than account equity, check the release calendar before holding through scheduled events, and use limit orders where the strategy tolerates the risk of no fill.
