Key takeaways
- Last look is a brief final window in which a provider accepts or rejects a trade request against a price it streamed.
- It exists to protect providers against stale quotes and latency arbitrage, which can support tighter streamed prices.
- The concern is asymmetric or lengthy last look — long hold times or checks that reject only when the market moves against the provider.
- Firm liquidity is immediately executable with no accept-or-reject step, offering higher fill certainty.
- Assess providers on fill ratios, hold times, symmetry and effective spread — not headline spread alone. The FX Global Code asks for disclosure of last-look practice.
Defining last look
When a liquidity provider streams prices, those prices are indications the provider is willing to trade on. In a last-look model, when a taker sends a request to deal on one of those prices, the provider does not fill it instantly. Instead it takes a short final window — often just milliseconds — to decide whether to accept or reject the request. Only after that check is the trade confirmed or declined.
Two checks typically happen inside that window. A price check asks whether the market has moved beyond an agreed tolerance since the quote was sent; a validity check confirms the request is well-formed and within credit and risk limits. If both pass, the trade is filled at the quoted price. Last look is widespread on streaming FX venues, but it is a defining feature of a provider’s model rather than a universal rule — firm liquidity has no such window.
Why last look exists
Last look emerged from the mechanics of streaming FX. A provider distributes quotes to many takers at once over networks with real, variable latency. In the time between a quote being sent and a request arriving, the market can move. Without any protection, faster participants could systematically pick off quotes that had become stale — a form of latency arbitrage — forcing providers to quote wider to compensate.
Used narrowly, last look lets a provider verify the quote is still valid before committing, which in principle allows it to stream tighter prices than it safely could otherwise. In that framing, a small, symmetric last-look window can benefit takers through better headline pricing. The debate is about how far that protection extends.
Pros, cons and the controversy
Last look is one of the more contested topics in FX market structure. The tension is straightforward: the same mechanism that protects a provider can, if applied unfairly, disadvantage the taker.
| Dimension | Potential benefit | Potential concern |
|---|---|---|
| Pricing | Supports tighter streamed spreads by limiting stale-quote risk | Tighter headline price may not translate into an equally good fill rate |
| Rejections | Filters genuinely stale or invalid requests | Asymmetric checks can reject mainly when the market moves in the taker’s favour |
| Hold time | A short window verifies price and validity | Lengthy hold windows can expose the taker to further market movement |
| Transparency | Disclosed, symmetric policies build trust | Undisclosed practice makes execution quality hard to assess |
Illustrative and structural. No fill ratios, hold times or spreads are shown or implied; actual practice varies by provider.
Industry attention — reflected in the FX Global Code, a set of good-practice principles for the wholesale FX market — has focused on making last look symmetric (applying price tolerance the same way whether the market moves for or against the provider), keeping hold times short, and disclosing how the check is used, including whether request information is used during the window.
Last look vs firm liquidity
Firm liquidity is the counterpart to last look. A firm price is immediately executable: when a taker hits it, it is filled without any further accept-or-reject decision, so there is effectively no rejection risk on that specific price. The trade-off is nuanced — firm liquidity gives higher fill certainty, while last-look liquidity may display tighter headline prices but carries rejection risk.
Because of that, headline spread alone is a poor way to compare providers. Desks typically look at the effective spread (what was actually achieved after rejections and any slippage) alongside fill ratios. A tight quote that is frequently rejected can be worse in practice than a slightly wider quote that fills reliably. How orders are handled once accepted is covered on our execution page, and the mechanics of building the book are in how FX liquidity aggregation works.
What to ask a liquidity provider
- Do you apply last look, and on which price streams? Where is firm liquidity available?
- Is your last look symmetric — is price tolerance applied the same way regardless of which side the market moves?
- What is your typical hold time, and is any request information used during the window?
- What fill ratios and rejection reasons can you evidence, and how is effective spread reported?
- Do you adhere to the FX Global Code, and can you share your disclosure?
For definitions of the terms used here, see the glossary, or read how a Prime of Prime aggregates and delivers institutional liquidity on full straight-through processing.
Frequently asked questions
What is last look in forex?
Last look is a practice in FX where a liquidity provider, after receiving a trade request against a price it streamed, takes a brief final moment to accept or reject that request before confirming the fill. During that window the provider typically runs a price check (has the market moved beyond a tolerance?) and a validity check. If the request passes, it is filled; if not, it can be rejected. Last look is common on many streaming FX venues but is not used on firm, executable liquidity.
Is last look good or bad?
Last look is neither inherently good nor bad — it depends on how it is used and disclosed. Used narrowly, it lets providers stream tighter prices by protecting them against stale quotes and latency arbitrage, which can benefit takers through pricing. Used poorly — with long hold times, asymmetric price tolerances that reject only when the market moves against the provider, or without disclosure — it can disadvantage the taker. The FX Global Code addresses these concerns and calls for transparency about how last look is applied.
What is firm liquidity vs last look?
Firm liquidity is immediately executable: a quote that, when hit, is filled without a further accept-or-reject decision, so there is effectively no rejection risk on that price. Last-look liquidity gives the provider a brief final window to accept or reject the request after it is received. Firm liquidity offers higher fill certainty; last-look liquidity may show tighter headline prices but carries rejection risk. Many desks assess providers on both fill ratios and effective spread, not headline spread alone. Talk to our desk to discuss your requirements.