At best order: FX execution instruction explained
By Ken Chigbo, Founder, KenMacro. Published 2026-05-13.
Quick answer
An at best order is an instruction to execute an FX trade immediately at the best price currently available in the market. It prioritises speed of fill over price certainty, meaning the trader accepts whatever liquidity sits at the top of the order book, including any slippage that may occur during volatile conditions.
What is at best order?
An at best order is a non-priced execution instruction sent to a broker or liquidity venue, directing it to fill the full size at the most favourable price currently quoted by counterparties. Unlike a limit order, no price cap is specified, and unlike a stop order, no trigger condition applies. The order works against the visible book the moment it arrives. In retail FX it functions almost identically to a market order, though some platforms distinguish the two by how unfilled residual size is treated. The instruction is common on voice desks and in algorithmic execution where immediacy outweighs price precision.
How traders use at best order
Retail traders use at best orders when speed of entry or exit matters more than locking in a specific price, for example reacting to a central bank statement or closing exposure ahead of a known event. The order is sent, the platform sweeps available liquidity, and the fill is reported back at one or several prices depending on size. Institutional desks use at best instructions when working a voice ticket with a single counterparty, or as part of an execution algorithm that has decided liquidity is sufficient to clear the block. The trade-off is slippage: in thin conditions such as the Asia handover or around major data prints, the realised average price can deviate meaningfully from the screen quote seen at the moment of submission.
Common misconceptions about at best orders
Traders often assume at best guarantees the price visible on the screen at the moment of clicking. It does not. The instruction guarantees execution against whatever liquidity is actually available when the order reaches the venue, which on a fast tape can be several pips away. A second misconception is that at best is safer than a market order because the name sounds protective. In practice the two behave the same on most retail platforms. Finally, at best is not the same as a fill-or-kill instruction: partial fills are usually permitted, and residual size may be cancelled or worked depending on the venue’s rules.
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Frequently asked
What is the difference between an at best order and a market order?
On most retail FX platforms the two are functionally identical: both instruct the broker to fill immediately at the best available price. The terminology differs by venue and by trading desk convention. At best is more common in voice trading and institutional execution, while market order is the standard label on retail platforms such as MT4, MT5 and cTrader. Both expose the trader to slippage, and neither guarantees the price displayed at the moment the order was sent.
Can an at best order be partially filled?
Yes. If the requested size exceeds the liquidity sitting at the top of the book, the order will sweep through successive price levels until either the full quantity is filled or the available liquidity is exhausted. Any residual size is typically cancelled rather than left working, though some institutional venues allow the unfilled portion to be re-quoted. The trader sees a volume-weighted average price across the levels that were hit.
When should a trader avoid using an at best order?
Avoid at best instructions during illiquid windows such as the late New York session, around the daily roll, or in the seconds following a major data release when spreads widen sharply. In these conditions slippage can be several multiples of the normal spread. A limit order, even one priced aggressively close to the market, gives price certainty and prevents adverse fills, though it carries the risk of missing the move entirely if the market trades through without filling.
Do ECN brokers handle at best orders differently from market makers?
Yes. On an ECN or raw-spread account, the at best order is routed against multiple liquidity providers and filled at the best aggregated price, with the broker adding a commission rather than marking the spread. On a market-maker account, the broker is the counterparty and quotes a single price that already includes its margin. Fill quality and slippage profiles therefore differ, with ECN execution typically offering tighter pricing in liquid hours but wider spreads in thin conditions.
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