Last Look: Detecting Hidden Costs in Forex Execution

A trader sees EUR/USD quoted at 1.08500, clicks 'buy', and the platform spins for 150 milliseconds. The order then returns with a 're-quote' or 'rejected' status, the market having moved to 1.08502. This is not simple slippage; it is the core experience of last look. It allows a liquidity provider (LP) or broker to review an order after it has been submitted but before confirmation, granting them a final decision to accept or reject the trade at the initially requested price. This decision window, often measured in milliseconds, is typically used to assess if the market has moved adversely against the LP since the quote was generated. This practice is inherent to the over-the-counter (OTC) nature of spot forex, where there is no central exchange to guarantee price and execution simultaneously. Unlike exchange-traded instruments where orders meet in a central limit order book, FX relies on bilateral relationships and quoted prices that are firm only until a counterparty decides otherwise. The prevalence of last look means that a displayed price is not always an executable price. The issue isn't merely the rejection; it's the asymmetry of information and optionality. If the market moves favourably for the LP, the trade is accepted at the old price. If it moves unfavourably, it is rejected or re-quoted, allowing the LP to offer a less advantageous price. This introduces a subtle, often unquantified, cost into a trader's execution.

Last look refers to a period, typically between 10 to 200 milliseconds, during which a liquidity provider or broker can withdraw a quoted price after a client attempts to trade on it. This period exists because generating a price, transmitting it, receiving a client's execution request, and then routing that request to the LP takes time. In highly liquid and volatile markets, prices can shift significantly within these brief windows. The official justification for last look is risk management for the liquidity provider. They need to ensure that the price at which they execute a trade for a client accurately reflects the price at which they can hedge or offset that exposure in the broader market. Without last look, LPs argue they would be forced to execute trades at prices that are no longer current, leading to guaranteed losses. However, the application of this right is where controversy arises. It is crucial to distinguish last look from simple slippage. Slippage occurs when an order is executed at a different price than requested because the market moved, but the trade was still filled. Last look, by contrast, gives the dealer the explicit option to not fill at the requested price, even if a fill was technically possible at a slightly worse price. The order is either accepted at the original price or rejected entirely, prompting a re-quote.

When a retail client places an order with a broker, that order typically goes through several stages. First, the client's platform sends the order to the broker's server. The broker then checks the client's margin and, if operating on an STP (Straight Through Processing) or ECN (Electronic Communication Network) model, sends the order to their liquidity providers. Market Maker brokers, who internalise client orders, perform an internal check against their own book and risk parameters. The 'last look' decision happens at the liquidity provider's end, or internally for a market maker, after they receive the order and before they confirm execution. During this brief window, their systems compare the requested price against the current market price they can obtain or hedge at. If the market has moved unfavourably, they can choose to reject the order or offer a new price (re-quote). This process is entirely automated and happens at machine speed. The critical aspect for traders is that this mechanism provides an asymmetric advantage to the liquidity provider. If the price moves in the LP's favour, the trade is accepted at the client's 'worse' requested price. If the price moves against the LP, the trade is rejected, forcing the client to re-submit at the new, worse price. This results in what is often termed 'negative slippage asymmetry', where slippage tends to be negative for the trader more often than positive.

The direct cost of last look extends beyond occasional rejected trades. It involves a persistent, subtle erosion of trading edge through adverse price adjustments. Over hundreds or thousands of trades, these small adjustments accumulate significantly. Imagine a trader aiming for a 5-pip profit on EUR/USD. If last look consistently causes 0.2 pips of negative slippage on accepted trades, or forces re-quotes at a 0.5-pip worse price, the strategy's profitability is severely hampered. A study analyzing millions of trades demonstrated that even with 'tight spreads' from some providers, the effective spread paid by clients, once last look effects were factored in, was higher. This effective spread includes the cost of rejections and the average price differential on accepted trades due to last look. A broker might advertise spreads starting from 0.0 pips on EUR/USD. However, if 20% of your trades are rejected during volatile periods, or filled at an average of 0.3 pips worse than the requested price, the advertised figure becomes misleading. For instance, a trade intended for 1.08500 might consistently fill at 1.08502 or 1.08503, even without a formal re-quote. This represents the subtle manifestation of last look: the LP's system 'accepts' the trade but at a micro-secondly updated, less favorable price. The difference between the quoted price and the actual fill price, when consistently skewed against the trader, constitutes the last look penalty.

Regulatory bodies such as the Financial Conduct Authority (FCA) in the UK and the Australian Securities and Investments Commission (ASIC) oversee broker conduct, including execution practices. Their focus is often on 'best execution,' a principle requiring brokers to take all reasonable steps to obtain the best possible result for their clients, considering factors like price, costs, speed, likelihood of execution, and size. While last look is not explicitly outlawed in all jurisdictions, regulators scrutinise its use. The FCA, for instance, has issued guidance on best execution, emphasising that firms must be able to demonstrate how they achieve it. The concern is that last look, when used unfairly, can violate these principles by consistently disadvantaging retail traders. Abusive last look practices, where a broker or LP systematically rejects trades when the market moves adversely but accepts them when it moves favourably, are considered unacceptable. The ESMA product intervention, capping leverage at 1:30 for retail clients, indirectly addressed some of the risks retail traders face, but it didn't eliminate execution risks like last look. Regulators expect transparency regarding execution policies. Traders should look for detailed disclosures from their brokers about how orders are handled and whether last look is employed by their liquidity providers. The absence of such clear disclosure should raise concerns.

Detecting last look requires meticulous analysis of executed trade data, often referred to as fill data or order history. The primary method involves comparing the price requested by the trader with the price at which the order was actually filled. This comparison, extended across a substantial number of trades, reveals patterns. If your fills consistently show negative slippage (i.e., you buy higher or sell lower than requested) more often and by a greater magnitude than positive slippage, it is a strong indicator of last look or similar adverse execution practices. Traders should export their complete trade history, including timestamp data for both order submission and execution. This allows for calculation of the execution latency. If execution times consistently correlate with negative slippage, it suggests the last look window is being exploited. For instance, if an order takes 100ms to execute, and during that 100ms, the price moves against you by 0.5 pips, and this is then the price you are filled at, it is problematic if favourable moves within the same latency result in fills at the old, less favourable price. Many trading platforms, such as MT4 and MT5, provide detailed execution reports. While not always easy to interpret, these logs contain the raw data required. Third-party analytical tools exist that can parse this data and highlight statistical anomalies in execution quality. This is the part most guides skip, expecting traders to simply trust the broker's 'fast execution' claims. In reality, it requires a quantitative approach.

Brokers typically operate under different business models that influence their execution practices. Market makers, such as XM and OANDA (though OANDA also aggregates liquidity), internalize client orders and profit from the spread or from clients' losses. They act as the counterparty to your trade and thus almost always retain the right of last look. This is a fundamental part of their risk management, allowing them to manage their exposure. Brokers advertising ECN or STP models, like Pepperstone and IC Markets, claim to route client orders directly to multiple external liquidity providers. These brokers often state they have 'no last look' policies. However, it is vital to understand that while they might not apply last look, their liquidity providers might. A broker's 'no last look' claim might simply mean they don't add their own last look layer, but they cannot guarantee that the underlying LPs don't apply it. This is a critical distinction often overlooked. Some hybrid models exist where brokers act as market makers for smaller trades and STP for larger ones. Traders must scrutinize the broker's terms and conditions regarding execution. The best brokers will provide clear, unambiguous statements about their order handling procedures and whether any form of last look is applied, either by them or their upstream LPs. Lack of clarity here usually signals a red flag.

While last look is a pervasive feature of OTC FX, traders can adopt strategies to mitigate its impact. The first is to select brokers with transparent execution policies and a verifiable history of good execution quality. This means looking beyond headline spreads and investigating actual fill rates and slippage statistics, if available. Prioritise brokers regulated by stringent authorities like the FCA or ASIC, as these bodies tend to enforce stricter best execution guidelines. Another strategy involves using limit orders rather than market orders during volatile periods. A limit order guarantees your price but not your fill. If last look results in a re-quote, your limit order simply won't fill until the price returns to your specified level, or better. While this can lead to missed opportunities, it protects against adverse execution at worse prices. For market orders, specifying a maximum deviation (slippage tolerance) on platforms like MT4 can prevent fills at prices significantly worse than requested, though it may increase the frequency of re-quotes. Finally, consider trading during less volatile periods or with currency pairs that exhibit higher liquidity, as these conditions generally reduce the likelihood and magnitude of last look effects. High-frequency traders often develop sophisticated algorithms to detect and route around last look venues, but for retail traders, diligence in broker selection and order type management remains the most practical defence.

The era of simply trusting advertised spreads and execution speeds is over for serious traders. To effectively detect and minimise the impact of last look, a data-driven approach is essential. This means routinely downloading and analysing your complete trade history. Look for patterns in slippage, execution latency, and re-quote frequency across different times of day and market conditions. A consistently negative average slippage, especially during news events or periods of increased volatility, is a strong indicator that you are being affected by last look. Consider using third-party analytics tools or even building simple spreadsheets to track these metrics. Compare your execution quality across different brokers if you hold multiple accounts. This empirical evidence is far more valuable than any marketing claim. Should you identify consistent patterns of adverse execution that cannot be explained by general market conditions, documenting this data allows for informed communication with your broker, or, if necessary, a complaint to their regulatory body. The financial markets are complex, and the mechanisms that affect execution are often opaque. However, through rigorous data analysis and an informed understanding of practices like last look, traders can gain a clearer picture of their true trading costs and make more informed decisions about where and how they choose to execute their trades. Vigilance and data are your primary tools in this endeavour.