ADVANCED: COURSE 3 | LESSON 2
Execution quality: slippage, spread behaviour at news
Learning objectives
Define and measure slippage (positive and negative) and understand which order types are exposed to it and when
Explain why spreads widen around news and session transitions, and quantify what that does to stops, entries and strategy costs
Track your own execution statistics and adapt order choice, timing and strategy design to real execution conditions
The edge you keep is net of execution
Two traders can run the identical strategy and end the year with materially different results, purely through execution: when they enter, with which order types, at which hours, and how their stops interact with spread behaviour. At the Professional level, execution quality is a line item you measure, not a vibe. The costs are individually small — half a pip here, three pips at a news print — but they recur on every trade, and recurring costs compound against you exactly the way expectancy compounds for you. Recall the arithmetic from A3.1's quiz: a strategy earning +2.2 pips gross per trade can lose most of its edge to real-world execution without a single rule failing.
Slippage: the difference between decision and fill
Slippage is the difference between the price you requested (or your order's trigger level) and the price you actually received. It is not inherently a defect — it is the mechanical consequence of the microstructure in A1.3: your order consumes whatever liquidity exists when it arrives, and the book at that instant may not contain your price.
Key distinctions. Market orders and triggered stops are exposed to slippage by construction: a stop-loss becomes a market order when touched, and fills at the best available price — which, in a fast market, can be far from the trigger (recall the 18-pip news example in A1.3). Limit orders cannot fill worse than their price; their cost is non-execution — the market may run without you. This is the fundamental execution trade-off: certainty of fill versus certainty of price. Slippage is signed: in fast markets you will also receive positive slippage (a better fill than requested) from brokers that pass improvements through. Over many trades, roughly symmetrical slippage in quiet conditions plus systematically negative slippage in fast conditions is the honest, expected pattern; measure yours rather than assuming either fairness or foul play.
Where negative slippage concentrates: scheduled news releases, session transitions and the daily rollover, weekend gaps (a stop held through Friday's close fills at Monday's open, wherever that is — the 2015 Swiss franc de-pegging remains the canonical extreme, gapping through stops by thousands of points), and large orders relative to available depth.
Spread behaviour: the heartbeat you trade inside
The spread is not a constant; it is a live risk gauge. EUR/USD might quote 0.6–1.0 pips through the London–New York overlap, 1.5–2.5 in late Asia, and spike to 5–15+ pips for a few seconds around a tier-1 release as liquidity providers pull quotes to avoid being picked off (A1.3). Crosses and exotics scale everything up.
Three practical consequences traders under-appreciate:
- Spread-triggered stops. Your stop-loss on a long is triggered by the bid. If price sits 4 pips above your stop and the spread momentarily widens by 6 pips at a release, your stop can trigger with the mid-price never having approached it. This is routinely misread as broker malfeasance; it is usually the documented mechanics of quoted spreads meeting a stop placed inside the news-widening radius.
- Costs scale with widened spreads. A strategy that trades the first minute after news pays the widened spread on entry — a 6-pip spread on a trade targeting 15 pips needs to be right about direction and magnitude just to overcome its entry cost.
- Effective vs quoted spread. What you actually pay (your fill versus the mid at decision time, plus commission on raw-spread accounts) is the number that belongs in your strategy's cost model — comparing account types (wider spread/no commission versus raw spread/commission) is a per-strategy arithmetic exercise, not a slogan.
Measuring your own execution
You cannot manage what you do not log. For every live trade, record: order type, requested/trigger price, fill price, signed slippage in pips, spread at entry and at exit, and a timestamp. (MT4/MT5 account history plus a few journal columns covers this; the A2.3 dashboard can host the analysis.) After 50–100 trades, compute: average signed slippage by order type; slippage distribution by hour and by proximity to scheduled news; effective spread by session; and the total execution cost as a percentage of gross edge. Typical findings that pay for the effort: one session quietly costs double the spread of another for the same setup; stop slippage clusters entirely within two minutes of releases; a "cheap" account type is expensive for your particular trade frequency.
Then adapt — this is where measurement becomes money. Prefer limit entries in thin hours and at pre-planned levels (A1.4's zones make this natural); avoid resting tight stops through releases you flagged in the A1.5 calendar step — widen beyond the news radius with size reduced to keep R constant, or go flat; if you must trade news reactions, accept market-order slippage as a modelled cost, not a surprise; and route strategy-level conclusions back into design (A3.1): a system whose edge is 3 pips cannot trade instruments and hours where execution costs 2.5.
The broker's side of the ledger
Understanding the mechanics also tells you what to ask of any broker, including us: published execution statistics (fill speeds, positive/negative slippage shares), transparent handling of stops at news, raw-spread account options with explicit commission, and no requotes on market execution. Regulators increasingly require execution-quality disclosure precisely because these numbers, not marketing, are the product. A professional reads them the way they read a backtest: sceptically, quantitatively, and with their own logged data as the cross-check.
Key takeaways
Slippage is microstructure, not malice: market orders and triggered stops take the book as they find it; limits fix price but risk non-execution
Negative slippage concentrates at news, rollover, session transitions and weekend gaps — the same clock that A1.3 mapped for liquidity
Spreads widen sharply for seconds around releases; stops placed inside the widening radius can trigger on the spread alone, and entries pay the widened cost
Log slippage and effective spread per trade; after 50–100 trades the statistics will tell you which hours, order types and account structures your strategy can afford
Execution cost is part of strategy design: model it in backtests (A3.1), budget it in expectancy (A2.3), and route around its hotspots via the weekly calendar (A1.5)