Order execution is the difference between the trade you request and the trade your broker actually completes. A narrow advertised spread tells you little about the final result if the order fills at a worse price, gets rejected or takes longer than expected.
When assessing forex brokers in the UK, examine pricing and execution together. The useful questions are practical: what price was available for your order size, how was the order handled, and what did you pay after commission and slippage? This guide focuses on those questions for retail forex derivatives, rather than currency exchange for travel or payments.
How a Forex Order Reaches Its Execution Price
A trade has several stages: your platform sends an instruction, the broker receives and checks it, and the order is filled or rejected under its execution arrangements. The price displayed when you click and the price available when your instruction arrives need not be identical.
Spot foreign exchange is not organised around one central exchange with a single universal price. Trading takes place across dealers and venues, including internal dealer liquidity pools. The BIS analysis of FX execution and market structure documents this decentralised arrangement. Treat a quote from another platform as a useful comparison, not automatic proof that your broker could execute your order at that price.
For an execution review, separate three timestamps where records allow: when you submitted the order, when the broker received it, and when it filled. A slow acknowledgement on your screen is not necessarily the same as a slow fill. Ask which interval any advertised execution speed measures before comparing figures.
Market Maker, STP and ECN Labels
A market maker deals as principal, taking the other side of the client contract. STP refers to straight through processing; ECN refers to an electronic communications network. These descriptions address different aspects of trading arrangements, so they are not interchangeable quality ratings.
Rather than choosing by acronym, ask whether the broker is your contractual counterparty, whether orders are routed elsewhere, and whether external transactions are your orders or the broker’s hedges. Request the relevant contract wording. “No dealing desk” is not a substitute for an explanation of how your price is determined.
Slippage Can Help or Hurt Your Trade
Slippage is the difference between an expected or reference price and the execution price. Negative slippage makes the fill worse for you; positive slippage improves it. Latency and volatility can contribute to either outcome. Passing adverse movements to clients while retaining favourable movements is a different issue: asymmetric slippage, examined in the FCA review of best execution and price slippage.
Consider a hypothetical purchase of £100,000 against US dollars. The displayed GBP/USD ask is 1.27000, but the order fills at 1.27008. The difference is 0.8 pip, costing $8 more than the displayed ask. A fill at 1.26994 would instead improve the price by 0.6 pip, worth $6.
The direction reverses for a sale. Selling at a higher price is favourable; selling at a lower price is adverse. Keep that distinction consistent in a trading journal or the figures can tell the opposite story.
One poor fill does not establish misconduct. Equally, repeated adverse fills deserve more than a generic “market conditions” reply. Compare similar order types, sizes and trading periods before deciding whether a pattern needs investigation. Do not assume positive and negative slippage should occur equally often: that expectation needs evidence about the orders being compared.
Market Orders, Limit Orders and Stops Make Different Trade-Offs
The basic distinction is between requesting prompt execution and setting a price boundary. A market order does not guarantee its execution price. A limit order specifies a price or better but may remain unfilled. A conventional stop becomes a market order once triggered. These distinctions also appear in the SEC investor guide to order types, which covers securities; check your forex provider’s terms for its precise implementation.
| Order instruction | What it prioritises | Main execution risk |
|---|---|---|
| Market order | Execution at available prices | The fill may differ from the displayed quote. |
| Limit order | The stated price or better | The order may not fill, or may fill only partly. |
| Conventional stop | Activating an order at a trigger level | The execution price may be worse than the trigger. |
| Stop-limit order, where offered | A price boundary after activation | The order may remain unfilled after triggering. |
Suppose a long GBP/USD position has a conventional stop at 1.2650. If the next executable bid after a gap is 1.2638, a hypothetical fill there is 12 pips below the trigger. A stop-limit instruction might prevent that execution, but it could leave the position open instead. Neither choice removes risk; each handles a different risk.
Before relying on a stop, ask which price triggers it: bid, ask or another defined reference. Also check whether your chart displays that same price. A screenshot of only one side of the market cannot, by itself, resolve every stop dispute.
Broker Pricing: Measure the Cost You Actually Receive
For a practical comparison, keep the spread, commission and slippage separate. The spread is the gap between bid and ask. Commission is an explicit charge. Slippage measures movement between your chosen reference and the fill. Mixing them carelessly can count the same cost twice.
Use a consistent reference. Compare a buy fill with the executable ask and a sell fill with the executable bid when measuring slippage from the quote. Comparing a buy fill with the midpoint also includes half the spread, so it answers a different question.
Account structure belongs in this calculation, but it is not the whole calculation. The comparison of standard and raw spread accounts covers how spread markups and separate commissions affect advertised costs.
A Worked Cost Comparison
Assume two hypothetical accounts trade the same GBP/USD position, worth $10 per pip. Ignore financing and currency conversion, assume unchanged spreads, and measure slippage against the relevant bid or ask on each side.
Account A has a 0.2 pip spread and charges $7 commission for opening and closing the position. Its baseline round-trip cost is $2 plus $7, or $9. If entry and exit each incur 0.3 pip of adverse slippage, another $6 raises the total to $15.
Account B has a 1.0 pip spread, no separate commission and no slippage in this example. Its round-trip cost is $10. Account A advertised the narrower spread but produced the more expensive trade.
This is arithmetic, not a forecast or a broker ranking. Repeat the comparison using representative records. One unusually good fill is no more reliable than one unusually bad fill.
What UK Best Execution Rules Require
Under the FCA’s COBS 11.2A best execution rules, firms must take all sufficient steps to obtain the best possible result, considering price, costs, speed, likelihood of execution and settlement, size and other relevant factors. For retail clients, the result is assessed in terms of total consideration: price plus costs directly related to execution.
The rules also require firms dealing in OTC products to check the fairness of the proposed price using market data and, where possible, comparable products. Dealing against the broker’s own account does not itself remove the best execution obligation.
Best execution is not a promise that every trade will match the best quote visible anywhere. It concerns the firm’s arrangements and conduct, not a guarantee against changing prices. Firms must provide appropriate execution-policy information, including a retail summary focused on total costs.
Read that policy as an operating document. Look for answers about pricing sources, execution venues, rejected orders, partial fills, price improvement and unusual market conditions. If the language does not explain what happens to your order, ask for clarification before depositing funds.
Requotes, Rejections and Last Look
When reviewing an unsuccessful order, establish whether it was rejected outright, returned with a new quote for acceptance, or partly filled. Those outcomes require different follow-up actions. Do not submit a replacement instruction until you know whether any exposure already exists.
In wholesale FX, “last look” gives a liquidity provider a final opportunity to accept or reject a trade request at its quoted price. Principle 17 of the FX Global Code’s execution principles calls for transparency and confines last look to validity and price checks. The Code is voluntary wholesale-market guidance, not a replacement for UK retail regulation.
If a broker refers to liquidity-provider rejection, ask how that event affected your client order. Did the broker reject it, try another provider, or execute at a different price? Also ask whether the same handling applies when the price moves in your favour.
A claim of “no requotes” answers only one question. You still need to know what happens instead, including whether the order can slip, be rejected or receive a partial fill.
How to Review Your Own Execution Records
Start with existing records rather than placing unnecessary trades to gather data. Choose a period covering the currency pairs, order sizes and trading hours relevant to your strategy. Keep scheduled news trades separate from routine entries so that one group does not disguise the other.
A useful review file should contain:
- Order ID, currency pair, direction, size and order type.
- Submission, receipt and fill timestamps where available, with the time zone recorded.
- The reference bid or ask, execution price, spread and commission.
- Positive or negative slippage, rejected requests and partial fills.
- Any news release, connection issue or platform message associated with the order.
Prioritise exportable records when assessing forex trading platform features. A clear audit trail is more useful for an execution dispute than another chart colour scheme.
Calculate average adverse slippage and average favourable slippage separately, then assess the combined effect. Also inspect the worst fills and rejection rate. An average alone can conceal occasional outcomes large enough to damage a strategy.
Record your benchmark honestly. If you have only the screen price when you clicked, label the result as a comparison against that price. Do not present it as proof of the price available when the broker received the order.
For published execution statistics, ask what the sample includes. Are rejected orders excluded? Are stop orders grouped with market orders? Does the quoted speed start at your device or at the broker’s server? Without matching definitions, two impressive figures may describe different things.
When an Execution Problem Needs Escalating
For a disputed fill, send the broker a concise written request with the order ID, timestamps, requested price and actual result. Ask for the relevant bid and ask history, the trigger event where applicable, and an explanation tied to the execution policy.
Describe the issue precisely. “My sell stop triggered although my chart stayed above it” is a question that can be investigated. “The platform stole my trade” supplies emotion but little evidence. Preserve trade confirmations, platform logs and the response rather than relying on screenshots alone.
Use unresolved discrepancies as part of your wider comparison of UK forex brokers. Assess whether the firm explains its records clearly and whether repeated outcomes fit its stated policy.
The aim is not to find a broker promising that prices never move. It is to establish how orders are priced, what happens when execution goes wrong, and whether the final costs suit the trades you intend to place. Judge the completed transaction, not just the spread beside the buy button.