You click "buy" on EUR/USD at 1.08500. The confirmation comes back at 1.08535. Nothing crashed and nobody re-quoted you by hand — you have just experienced slippage, and understanding it is one of the clearest ways to tell how a broker actually handles your orders.

Slippage is the difference between the price you expected when you submitted an order and the price at which the order actually filled. It is not a broker fee and it is not charged on a statement. It still costs money: the U.S. National Futures Association defines it as the price difference between when an order is submitted and when it reaches the broker's system, and notes that since the dealer typically takes the other side, an unfavorable move for you is a favorable one for the dealer (NFA Interpretive Notice 9064).

Why slippage happens

Three forces drive nearly every slipped fill:

• Latency. Your order takes milliseconds to travel from your device to the broker's system. In that window the market can move. On a calm major pair this is usually a fraction of a pip; around news it can be several.

• Liquidity gaps. Your order fills at the next available price level, not your requested one. If there are no resting orders at 1.08500, you get the best price that actually exists.

• Price gaps. Prices can skip entire levels — over a weekend, at the daily open, or on a data release. If a gap jumps over your price, your fill lands on the far side of it.

Volatile moments are where slippage concentrates: major data releases, central bank decisions, and thin sessions such as the market open on Monday morning. In quiet conditions on liquid pairs, most market orders fill within a fraction of a pip of the quote.

Positive and negative slippage

Slippage is not always against you:

• Negative slippage — a buy fills higher than expected, a sell fills lower. This raises your cost or deepens your loss.

• Positive slippage (price improvement) — a buy fills lower or a sell fills higher than requested. Brokers and educators describe this as a normal outcome too, not a myth (OANDA education on slippage and execution risk).

Both directions are normal in live trading. What matters for comparing brokers is whether both directions are passed through fairly — more on that below.

Stops, gaps, and the cost nobody budgeted

A stop-loss order does not guarantee an exit price. Once triggered, it effectively becomes a market order: in a fast market or through a gap, it can fill somewhere worse than the stop level. As Saxo puts it, stop-loss orders "help limit losses, but they don't guarantee the execution price" (Saxo on stop-loss orders).

This is where slippage turns from a nuisance into a risk-management problem. If you sized a position for a 20-pip stop and a gap fills you 45 pips away, your realized loss is more than double what your plan assumed. Some brokers offer guaranteed stop-loss orders that fill at the exact level regardless of gaps — usually at a cost, such as a wider spread or a fee, and availability varies by broker and jurisdiction. Check the specific terms rather than assuming the feature exists.

How brokers are supposed to handle it — and where rules actually apply

Handling of slippage is regulated in some markets. The clearest example is the United States, where forex dealers (FDMs) regulated by the CFTC and NFA must follow specific rules. NFA's Interpretive Notice 9064, issued after disciplinary cases, establishes that:

• Dealers must apply slippage settings symmetrically. Filling orders that moved against the customer while rejecting orders that moved in the customer's favor — or passing only negative slippage to the customer — was found in disciplinary complaints to violate NFA rules against deceptive and manipulative practices.

• Dealers must disclose their slippage policy before the first forex transaction: whether stale-priced orders execute automatically at the current price or the customer is asked to accept or reject the new price, and what slippage parameters, if any, apply.

• A dealer that advertises a platform with "no slippage" must actually be designed to execute market orders at the displayed price.

These are U.S. retail-forex rules. Other jurisdictions have their own conduct standards (for example, best-execution obligations in EU/UK regimes), but the specifics differ — do not assume NFA-style symmetric-slippage requirements apply to every broker or every account.

A practical checklist for reducing execution surprises

• Use deviation or limit settings. Most platforms let you set a maximum deviation on market orders or use limit orders that cannot fill worse than your price (at the cost of possibly not filling at all).

• Trade liquid pairs in liquid hours. Majors in the London/New York overlap slip far less than exotics at 3 a.m.

• Avoid known volatility windows if your strategy does not need them — the minutes around top-tier data releases produce the largest gaps.

• Treat slippage as a transaction cost. Like spread and commission, it belongs in your strategy math. OANDA frames it as an inevitable variable cost that must be monitored rather than dismissed as bad luck (OANDA education).

• Read the broker's slippage/order-execution disclosure before depositing. Whether they publish one at all, and how specific it is, is itself information.

• Be skeptical of "zero slippage" marketing. If a platform truly never slips, its quotes and fills need to match by design — which is a strong, checkable claim.

An illustrative cost example

Illustrative example, not a broker quote or forecast. Suppose you buy one standard lot of EUR/USD (100,000 units; 1 pip = 0.0001; pip value ≈ $10 per standard lot) with a requested price of 1.08500 and fill at 1.08535:

• Slippage = (1.08535 − 1.08500) / 0.0001 = 3.5 pips

• Cost = 3.5 pips × $10/pip = $35 on that trade

Now suppose a short-term strategy targets a 5-pip gross edge per trade but averages 1.5 pips of negative slippage per fill. Over 20 trades: expected gross 100 pips, slippage 30 pips, net 70 pips — a 30% haircut that never appears as a line item. This is why backtests that ignore slippage routinely overstate live results: demo fills at the requested price hide the cost entirely (computed example using standard pip-value convention; your broker's pip value and typical slippage may differ).

Frequently Asked Questions

Is slippage the same as spread?

No. Spread is the visible difference between bid and ask — a cost you can see before trading. Slippage is the difference between your requested price and your actual fill, caused by movement and liquidity during execution.

Can slippage be positive?

Yes. When price moves in your favor between request and fill, you get price improvement. Broker rules in regulated markets generally require both directions to be treated symmetrically.

Why did my stop-loss lose more than I planned?

A stop-loss converts to a market order when triggered. In a fast market or across a gap, the next available price can be well past your stop level, so the fill — and the loss — is larger than planned.

How do I know if a broker handles slippage fairly?

Read its order-execution disclosure: how stale-priced orders are handled, whether slippage parameters exist, and whether they apply in both directions. In the U.S., NFA rules require this disclosure before your first trade and prohibit asymmetric slippage settings.

Practical next step

Before choosing a broker, check how it discloses slippage handling and execution statistics, and review your own fill history for how often and how far fills deviate from quotes. Comparing execution practices is part of comparing total cost — the same idea behind comparing spreads and commissions.