// GLOSSARY

Sweep the book

Executing through multiple price levels at once — taking all available liquidity up (or down) to some price. Buys certainty of fill at the cost of walking the book: each successive level fills worse, and the market is left visibly moved.

To sweep is to trade through the book rather than at it: one aggressive order that clears the first level, then the second, then the third, until your size is done or your limit is hit.

Worked example

The ask side shows 300 at 44¢, 400 at 46¢, 500 at 49¢. A sweep of 1,000 contracts fills 300 + 400 + 300 across three levels for an average of about 46.3¢ — 2.3¢ over the touch — and leaves 49¢ as the new best ask for everyone watching. On Kalshi, the taker fee applies to every contract on top.

When sweeping is right

Sometimes! If your signal decays in seconds — a resolution-relevant headline, a cross-venue arbitrage about to close — paying 2–3¢ for certainty beats watching the opportunity vanish while a sliced order grinds. The discipline is making it a choice with a price cap (an IOC at your walk-away price), not a default. The cost math is worked through in slippage in thin prediction markets.