Kalshi Fees Peak at 1.75% at 50/50: Maker vs Taker
Prediction market prices come from a two-sided order book. Here is how maker and taker fees work, and why the posted rate is not the bill.
Published 2026-10-13 · Data as of 2026-10-13 · Market & data intelligence · Educational, not advice.
On Kalshi and Polymarket, prices come from an order book where users trade each other, not a house. Makers rest orders and pay little or nothing; takers cross the spread and pay more. Kalshi's taker fee peaks at 1.75 percent at a 50/50 price. But the spread you cross is a hidden cost the fee schedule never shows.
On Kalshi and Polymarket, every contract pairs two people on opposite sides of a position. No venue quotes it, and no house takes the other side. Understanding that one fact explains the fees, the spread, and why the number on the screen is not quite the number you pay.
The order book sets the price, not the venue
Polymarket's documentation is blunt about this: prices are not set by Polymarket, they emerge from supply and demand as users trade with each other. Trading runs on a central limit order book — a running list of what buyers will pay and what sellers will accept.
The matching is tidy because the contract is binary. When a buyer of Yes at $0.60 meets a buyer of No at $0.40, Polymarket converts the combined $1.00 into one Yes share and one No share, each going to its buyer. Every position therefore has a counterparty holding the other side. Your Yes exists only because someone wanted the No.
Kalshi describes the same symmetry from the order-book side. In its API documentation, a Yes bid at price X is the identical order to a No ask at $1.00 minus X, because the two sides of a binary contract always sum to a dollar. One resting order is two offers at once.
What gets shown as the price is itself a choice. Polymarket displays the midpoint between the best bid and the best ask — except when that spread is wider than $0.10, where it shows the last traded price instead. The mid is a convenience, not a price you can necessarily trade at.
Makers, takers, and who actually pays
The order book splits every participant into two roles. A maker, in Kalshi's fee documentation, is an order that is not matched immediately and instead rests on the book. A taker crosses the spread and trades against a resting order. Makers add liquidity; takers remove it. Kalshi charges a maker fee only if the resting order later trades, and canceling an unfilled resting order costs nothing.
The price of those two roles differs sharply. Kalshi's fee schedule, effective July 7, 2026, charges takers round-up(M × 0.07 × C × P × (1 − P)), where C is the contract count, P the price in dollars, and M a multiplier that defaults to one. Makers on the same schedule pay round-up(M × 0.0175 × C × P × (1 − P)) — one quarter of the taker rate.
Notice the P × (1 − P) term. The fee is largest when P is 50 cents and shrinks toward either extreme. At 50/50 the taker fee works out to 1.75 cents per contract before rounding. Delta Arc's venue map records the same shape: Kalshi's fee peaks at 1.75 percent at a 50/50 price and falls away as a contract approaches a penny or a dollar.
Polymarket's fee page uses the same mathematical shape — fee = C × feeRate × p × (1 − p) — with a 0.05 taker rate on sports markets, and only takers pay it: makers are never charged. Polymarket's own worked example puts the taker fee on 100 sports shares at $1.25 when the price is $0.50, and $1.05 at either $0.30 or $0.70. Its sports markets also return 15 percent of collected fees to makers as rebates — a direct subsidy for resting liquidity.
The posted fee is not the all-in cost
Here is the part most comparisons miss. A headline fee rate describes only one line of the bill. Delta Arc's venue map found that a spread four cents wider on a low-fee venue costs more than a 1.75 percent fee on a tight book. The spread you cross is a cost too, and it does not appear on any fee schedule.
That gap can be large. In a 192-day Kalshi study of S&P 500 year-end brackets, Delta Arc found that building a position in P(≥7,500) from the individual brackets cost about 0.75 at the asks, against an options-implied value near 0.64. The mid can lean one way while the ask quietly closes the door.
So the next time a price looks cheap, ask three questions: maker or taker, how wide is the spread, and whose book am I really on. Delta Arc's Prediction Markets product shows the live board across Kalshi and Polymarket in one place, which is where those three answers start to line up. The all-in cost lives in the gaps between them.
Sources: Polymarket Documentation, Prices and Orderbook; Kalshi API Documentation, Orderbook Responses; Kalshi Help Center, Fees; Kalshi Fee Schedule; Polymarket Documentation, Fees; Delta Arc research.
Sources
Outside pages cited in this post, in order of first citation
- Polymarket's documentationdocs.polymarket.com
- API documentationdocs.kalshi.com
- fee documentationhelp.kalshi.com
- fee schedulekalshi.com
- fee pagedocs.polymarket.com
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