Taker
A trader who submits an order that immediately matches against resting liquidity, removing it from the order book.
Definition
A taker is a market participant whose order crosses the spread and matches against a resting limit order on the book. By taking liquidity, the taker enables an immediate trade but pays a fee in exchange. The taker's order is typically submitted as a FOK or IOC instruction so it never rests on the book.
In practice
On Polymarket, the taker fee depends on the contract type and price level. For 5-minute crypto binaries, the peak taker fee reaches roughly 1.56% at $0.50 probability. A scalper bot that buys YES at $0.50 and needs YES to move to $0.52 to break even must account for both legs of taker fees. Strategies like poly5m-v1 and poly5m-v2 are pure taker strategies, relying on Binance price-change signals to enter and exit before the fee erodes the edge.