Multi-leg execution

Multi-leg execution is the act of sending several orders together that depend on each other so you can lock a position.

On Polymarket this commonly appears when you need to buy or sell multiple outcomes simultaneously — for example, the YES and NO legs of a binary intra-market arbitrage or the complete set of outcomes in a multi-outcome market. The goal is to execute all necessary trades as a coordinated unit so the net exposure is a known, bounded quantity rather than an unintended directional bet.

Key takeaways

• Multi leg execution groups dependent orders so the combined position is deterministically defined.
• It's essential for intra-market arbitrage where you must capture a spread by buying multiple outcomes together.
• Execution risk (partial fills, timing) and oracle resolution risk still apply; the spread is not unconditionally risk-free.

How it works on Polymarket

Polymarket uses a CLOB for matching. To perform a multi-leg execution you either:

• Submit multiple orders in quick succession through a single client (the common approach for simple two-leg binary arbitrage), or
• Use a builder or execution engine that routes and attributes orders while coordinating fills.

Many bots and tools implement atomic-looking behaviour by sending legs rapidly and cancelling unmatched legs when fills are partial. On Polymarket the CLOB and the Relayer make order placement gasless; the system supports FAK (Fill-And-Kill) orders which are often used for legs where immediate execution or cancellation is required.

Risks and failure modes

• Partial fills: If some legs fill and others do not you can be left with an unintended directional exposure.
• Slippage and fees: Execution prices can move while your legs are in-flight; taker fees apply and vary by category.
• Resolution and settlement: UMA disputes or delayed resolution can affect final payout timing. Redeeming outcome tokens requires CTF operations (split/merge/redeem) and settlement timing can vary.
• Geo and compliance limits: Polymarket blocks or restricts orders by jurisdiction; you must comply with Polymarket's geographic rules.

Best practices

• Use FAK orders for legs that must execute immediately or not at all.
• Monitor orderbook depth and midpoint to size legs conservatively relative to available liquidity.
• Implement clear recovery rules for partial fills (e.g., hedging, cancelling, or opportunistic unwind).
• Account for fees and slippage when computing whether the combined legs create sufficient edge.

How this affects your trading

If you rely on intra-market arbitrage, multi leg execution is operationally central: your strategy's profitability depends as much on how you place and coordinate legs as on identifying price discrepancies. Design your execution logic to minimise partial fills, include post-trade reconciliation, and treat spreads as mathematical opportunities that still carry settlement, slippage, and resolution risk.

See also

• /glossary/leg-risk
• /glossary/fak