Taker fee (prediction markets)
The fee a prediction market charges when your order fills against resting liquidity — Kalshi and Polymarket both charge takers, scaled by price × (1 − price).
Kalshi charges 7% × contracts × price × (1 − price), rounded up to the cent, on most series. Polymarket charges size × category rate × price × (1 − price), with rates around 4–7% depending on category, and charges makers nothing. Both formulas peak at 50¢ (about 1.75¢ per contract on Kalshi) and shrink toward 0 near 1¢ or 99¢.
Fees are charged on the trade, not on winnings, and are the reason a visible cross-venue gap of 2–3% often nets to zero. ArbMonster prices every leg with the venue's exact schedule.
Measured on ArbMonster: Kalshi fee calculator · Polymarket fee calculator · Every venue's real cost
Related terms: Maker fee / maker rebate · Net edge · Arbitrage