Fill-or-Kill Order

Detailed explanation

A fill-or-kill (FOK) order is an order that must be executed in full or not at all. If the entire quantity cannot be matched immediately against the order book, the order is cancelled without any partial fill. This helps traders lock in a precise execution outcome and avoid partial exposure in a fast-moving market. On Kalshi, standard order types include limit and market orders, and FOK operates as an all-or-nothing instruction within the CLOB and clearing rules.

In practice, an FOK on a binary market ensures you either acquire the full amount of YES and/or NO you intended (if supported as a single cancel-if-not-filled instruction) or you avoid entering a position entirely. This can affect edge capture, especially when spreads tighten or when liquidity is thin around a given contract. Remember that Kalshi charges per-contract fees, and FOK behavior interacts with current liquidity, best bids/asks, and settlement timing as dictated by Kalshi’s rulebook.