Last Look Execution

Last look execution is a practice in which a liquidity provider, having streamed a quote, keeps a brief window to accept or reject an incoming order after seeing it. If the market has moved against the provider during that window, the order can be rejected or re-offered at a new price. The practice exists because streamed prices are indicative and providers want protection against latency arbitrage. For the trader, last look appears not as a fee but as rejections, requotes or slippage, and it matters most to strategies that depend on fast fills. Execution models differ: some venues and providers stream firm, no-last-look prices, and brokers increasingly state in their execution policy whether last look applies. What to check: a broker’s execution policy is where last look is disclosed, and the useful details are the length of the window, whether the check is symmetric — rejecting moves in both directions rather than only those against the provider — and what happens to a rejected order. Your own fill data answers the rest. A rising rejection rate, or slippage that lands against you far more often than for you, is the practical signature of the practice whatever the policy says.