Last look

Last look is typically associated with additional hold time (AHT). As such, AHT is also referred to as the last look window, last look hold time or order review time (ORT). The maximum configured duration for AHT on a venue is sometimes called the last look threshold. The realized delay associated with AHT is also sometimes called last look round trip time.

The original motivation of AHT is to allow LPs additional time to perform price validation, credit checks, and other risk or operational controls before responding to a trade request. Following these checks, the LP may accept or reject the trade in accordance with the last look protocol.

The practice of last look has drawn some criticism with the rise of electronic trading and non-bank LPs who are able to eliminate the use of AHT through better forecasting and low latency infrastructure. In contrast to centrally cleared markets, OTC markets like FX rely on bilateral credit relationships between counterparties, which has led market makers (liquidity providers) to adopt protective mechanisms like AHT and last look—often at the client’s expense.

While AHT and last look were initially intended as risk control mechanisms, in modern FX markets, LPs will usually the additional hold time to assess the profitability of a trade based on market data that arrives after the trade. Trades deemed unfavorable may be rejected in order to reduce adverse selection and mitigate market impact against the LP's own positions.

This practice introduces an information asymmetry, as the price taker (liquidity taker) submits their order or trade request on staler information than that available to the LP at the last look decision point. As a result, liquidity takers are more likely to receive fills on trades that perform poorly and to experience rejections on trades that would have been profitable, creating an implicit transaction cost.

Most venues impose a maximum AHT threshold set by the venue operator. In practice, the average realized AHT across trades is typically much lower than this maximum.

Many FX ECNs provide statistics on AHT and last look behavior to its participants. According to a CME Group publication, the average last look hold time on its EBS platform in 2022 was 12 milliseconds, while the maximum threshold was 200 milliseconds. As of 2025, the average last look hold time on the largest FX trading platforms is around 10 milliseconds. Given that pre-trade risk checks—such as those required under 15(c)3-5 in U.S. equities—can be performed with sub-microsecond latency, this implies that only a small fraction of AHT is attributable to risk or operational checks.

In recent years, there has been an industry push toward reducing or eliminating last look for purposes beyond risk management, as well as increasing transparency. In 2023, EBS reduced its last look threshold to 30 milliseconds. In 2025, Cboe FX (formerly KCG's Hotspot FX) reduced its threshold in two phases: from 35 milliseconds to 20 milliseconds on April 1, 2025, and then to 10 milliseconds on October 10, 2025. EBS also provides transaction cost analysis (TCA) tools that report AHT distributions across different percentiles. Some LPs, such as Goldman Sachs, have last look disclosure documents which are publicly available.

AHT adds a layer of complexity for the simulation of FX strategies on venues that support last look, as fill (rejection) rates cannot be modeled solely from historical price data. Accepted trades tend to exhibit worse realized performance for liquidity takers once the adverse selection effects of AHT and last look are taken into account.

Some buy-side participants therefore choose to trade exclusively on liquidity pools that do not employ last look or AHT. These venues are often described as central limit order book (CLOB), order-based, or order-cross-order (OXO) venues, in contrast to order-cross-price (OXP) pools that incorporate last look into quoted prices.

Liquidity pools without last look typically exhibit wider spreads and lower available volume. This is expected, as LPs can quote tighter apparent spreads when protected by last look and AHT.