Slippage, Requotes and Execution Quality: Is Your Broker Filling You Fairly
Most retail traders judge a broker by its spread and its sign-up bonus. They almost never check how they are actually filled. Execution quality is the part of a broker that costs you money quietly, trade after trade, in a way that never shows up as a line item. This guide is how an institutional desk thinks about slippage, requotes and fill quality, and the practical self-audit a retail trader can run to find out whether a broker is filling fairly.
Some slippage is normal and unavoidable. Asymmetric slippage is the red flag. Holding both of those at once is the entire skill, and most coverage holds neither.
The desk’s read, in one box
Slippage is the gap between the price you asked for and the price you got. Some of it is unavoidable: markets move in milliseconds and liquidity is finite, so fast and thin conditions and scheduled news will always produce slippage at any honest venue. The signal is not whether slippage exists, it is whether it is symmetric. Negative slippage that is common while positive slippage almost never appears is the real red flag. Requotes are a dealing-desk feature, a true agency model fills you instead. Judge the fill separately from the spread, and judge it across a large sample, not one bad trade.
What slippage actually is
Slippage is the difference between the price you requested and the price you were filled at. It exists for two structural reasons, and neither of them implies anything dishonest. First, price moves in the milliseconds between your order leaving the platform and reaching liquidity, so the price you clicked is already history by the time the order arrives. Second, the volume available at your requested price is finite, so a larger order eats into the next price levels and fills at a blended worse price. Both of these are properties of a live market, not defects in a broker.
This is why a venue that advertises zero slippage is making a claim that the structure of markets does not allow. The honest position is that slippage happens, it should be roughly two-sided, and the job is to measure the pattern.
Positive versus negative slippage, and why symmetry is the signal
Negative slippage is a worse price than you requested. Positive slippage is a better price than you requested. Both are real. At an honest venue routing to genuine liquidity, price can move in your favour in those milliseconds just as easily as against you, so over a large sample you should see positive slippage occur with meaningful frequency, not as a rare event.
This is the test that matters. A broker where negative slippage is routine and positive slippage almost never shows up is displaying asymmetry that the structure of markets does not produce on its own. One-sided slippage is the recognised footprint worth investigating. The raw existence of slippage is not. Most retail complaints fixate on the wrong half of that sentence.
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Requotes, and why a true ECN does not requote
A requote is when you submit an order at a displayed price and the broker, instead of filling you, rejects it and offers a new price to take or leave. Requotes are a feature of a dealing-desk or market-maker model, where the broker is the counterparty and prices your order against its own book, so it can decline the price you asked for.
A genuine ECN or STP model routes the order to external liquidity providers and fills you at whatever is available there. There is no internal book to reject against, so instead of a requote you get a fill, sometimes with slippage if price moved or size was thin. That is the structural reason pure agency execution shows slippage but not requotes. It also means no-requote marketing is a weaker signal than people think, because the more useful question is the slippage symmetry sitting behind it.
Latency and last-look liquidity
Two mechanics sit underneath fill quality and are worth naming. Latency is the time your order spends travelling from platform to liquidity and back. More latency means more room for price to move, which means more slippage, which is a structural cost rather than misconduct, though a venue with consistently poor infrastructure is still a venue filling you worse.
Last-look is a practice where a liquidity provider, after receiving your order at a quoted price, takes a brief final check and can reject it if price moved against the provider in that window. It exists across parts of the FX market and is not inherently abusive. The concern is aggressive last-look that produces a one-sided pattern, your good fills rejected and your bad fills accepted. You cannot observe last-look directly as a retail trader. You can see its footprint in your own fill log, which is the entire point of keeping one.
A wide spread is not the same as a bad fill
These get conflated constantly and the confusion leads to wrong conclusions. The spread is the quoted gap between bid and offer. You can see it before you trade, and it widens legitimately when liquidity is thin or volatility is high. A bad fill is execution worse than the conditions justify: heavy negative slippage with no offsetting positive slippage, or requotes on orders that should have filled cleanly.
The practical consequence is that a broker can run a headline-tight spread and still fill you badly, and a wider-spread venue can fill cleanly and cost you less in total. Spread is the advertised price. Fill quality is the price you actually pay. Judge them separately or you will pick a broker on the number that is easiest to market.
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The order types that protect you and the ones that expose you
Order choice changes how much execution risk you carry, especially around news.
- Limit orders fill at your price or better, never worse. They protect you from negative slippage at the cost of non-execution if price runs away from you.
- Slippage tolerance or maximum-deviation settings let you cap how much negative slippage you will accept on a market order. The order is rejected rather than filled beyond your limit. This is the single most under-used protection on retail platforms.
- Market orders into scheduled news are the maximum-exposure choice. You are asking to be filled at any available price in the thinnest, fastest conditions of the day. This is where one-sided slippage hurts most and where venue quality is most visible.
You cannot remove execution risk, but you can decide how much of it you are volunteering for. A trader who fires market orders into the payrolls release and then blames the broker has chosen the order type that maximises the very thing being complained about.
What an institutional execution review actually checks
On a desk, execution is reviewed as a measured cost, not a feeling. The review looks at requested versus filled price across a large sample, the symmetry of slippage rather than its existence, fill behaviour segmented by condition (calm, volatile, around scheduled releases, at the open), rejection and requote rates and whether they cluster on faster or more profitable orders, and the all-in cost including spread, commission and the slippage distribution rather than any single advertised number. The output is a distribution and a pattern, never a verdict from one trade.
Treat execution as a cost, not a feeling
Execution quality is one of the unglamorous inputs that decides whether an edge survives contact with a real account. Start with the free macro framework, then sit with the desk.
The self-audit a retail trader can actually run
You do not need a desk to do this. You need a log and patience.
- Record every fill. For each trade, log the requested price and the filled price, the time, and whether it was around scheduled news. Build a sample of dozens of fills before drawing any conclusion.
- Check symmetry. Count negative versus positive slippage. Honest agency execution produces positive slippage with real frequency. A near-total absence of positive slippage across a large sample is the signal.
- Segment by condition. Separate calm fills from news and open fills. Any venue slips more in fast conditions. An honest one still slips roughly two-sided.
- Watch the rejections. Note whether requotes or rejections cluster on your faster or more profitable orders specifically. Clustering is the pattern worth escalating.
- Hold the sample, not the anecdote. One bad fill is noise. A consistent one-sided pattern across many fills is information. Treat them differently.
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The mistakes that make execution analysis useless
Judging a broker on one bad fill instead of a distribution. Choosing on headline spread and never measuring the fill. Believing no-slippage and no-requote marketing instead of measuring symmetry, since the structure of markets does not allow zero slippage. Firing market orders into news and then blaming the venue for the slippage that order type guarantees. And the deepest one: never logging requested versus filled price at all, then having only feelings where there should be a sample. Execution quality is measurable. Most traders simply never measure it.
Related reading
- Forex trading costs explained (spread, commission, swap and where slippage sits in the total)
- How to choose a forex broker (the full broker-selection checklist this fits inside)
- How to verify a forex broker is legit (regulation and the checks before execution even matters)
- The free macro framework (the regime read that decides when you should be trading at all)
Frequently asked questions
What is slippage in forex trading?
The difference between the price you requested and the price you were filled at. It happens because price moves in the milliseconds before your order reaches liquidity, and because the size at your price is finite. Some slippage is normal and unavoidable, especially in fast or thin markets and around news. It can be negative or positive. The pattern, not the existence, is what tells you if you are filled fairly.
Is slippage always bad?
No. Slippage is a property of live markets, not a defect. When price moves and liquidity is thin, a market order fills at the next available price, worse or better. Positive slippage is real at honest venues. The thing to judge is symmetry: if negative slippage is common and positive almost never appears, that asymmetry is the signal, not the raw fact that fills move.
What is a requote?
When you submit an order at a displayed price and the broker rejects it and offers a new price to accept or decline instead of filling you. Requotes happen on dealing-desk models where the broker prices against its own book. A genuine ECN or STP model fills you at the available price, with slippage, rather than requoting. Frequent requotes on profitable or fast orders are a recognised complaint.
Why does a true ECN broker not requote?
It passes your order to external liquidity and fills you at whatever is available there. There is no internal book to reject the price against, so instead of a requote you get a fill, sometimes with slippage. Requoting is a dealing-desk feature. This is why agency execution shows slippage but not requotes, and why no-requote marketing matters less than the slippage symmetry behind it.
What is last-look liquidity?
A practice where a liquidity provider takes a brief final check after receiving your order and can reject it if price moved against the provider in that window. It exists across parts of FX and is not inherently abusive. Aggressive last-look produces a one-sided pattern: good fills rejected, bad fills accepted. You cannot see it directly but you can see its footprint in your own fill log.
How can I check my broker’s execution quality myself?
Log requested versus filled price for every trade over a large sample. Check three things: is slippage symmetric, how do fills behave around scheduled news and the open, and do requotes or rejections cluster on your faster or more profitable orders. One bad fill is noise. A consistent one-sided pattern across many fills is the thing that matters.
Is a wide spread the same as a bad fill?
No, and conflating them leads to wrong conclusions. The spread is the quoted bid-offer gap, visible before you trade, and it widens legitimately in thin or volatile conditions. A bad fill is execution worse than conditions justify, like one-sided negative slippage or requotes on orders that should have filled. A tight-spread broker can fill badly and a wider-spread venue can fill cleanly. Judge them separately.
Educational analysis only, not financial advice. Past performance does not guarantee future results. Always manage risk and never risk more than you can afford to lose. This is macro education and scenario framework, never a signal or a recommendation to trade.
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