Polymarket US’s September fee changes: straight trades, combos and rebates

Polymarket US raised its standard taker fee coefficient to 0.0695 on September 17, 2026, while leaving the maker rebate coefficient at −0.0125. The standard fee therefore peaked at $1.74 for a single fill of 100 contracts at 50 cents. September 25 brought a separate change to combo taker fees, not the effective date of the standard fee increase. Those dates are established by the exchange’s September 21 notification and September 29 filing.

This is a historical reference for Polymarket US order-book trades, not a live schedule or a schedule for the international platform. Block trades have a separate fee schedule.

Standard trades: the September 17 formula

For standard trades, the exchange used:

Fee = Θ × C × p × (1 − p)

Here, C is the number of contracts and p is the execution price in decimal dollars: a 50-cent trade uses p = 0.50, not 50.

• Taker: Θ = +0.0695, a charge for taking available liquidity.
• Maker: Θ = −0.0125, a rebate for providing the resting order that fills.

The September 17 amendment increased the taker coefficient from 0.06; the maker rebate and tiered taker rebates were unchanged. At the midpoint, that raised the exact fee for 100 contracts from $1.50 to $1.7375—an increase of about 15.8% before rounding. Source: exchange amendment.

The table below applies the September standard coefficients to a single 100-contract fill, before any taker rebate:

Execution price	Purchase value	Taker fee	Maker receives
$0.10	$10.00	$0.63	$0.11
$0.30	$30.00	$1.46	$0.26
$0.50	$50.00	$1.74	$0.31
$0.70	$70.00	$1.46	$0.26
$0.90	$90.00	$0.63	$0.11

These amounts match the official standard-price table. The dollar fee is symmetric: prices of 10 cents and 90 cents produce the same charge. 0.0695 is a coefficient, not a flat 6.95% charge on purchase value. Ignoring rounding, a buyer’s taker fee divided by purchase value is 0.0695 × (1 − p).

September 25: combos acquired a different curve

At 12:00 a.m. ET on September 25, the combo taker formula changed to:

Fee = C × p × [0.0695 × (1 − p) + 0.04 × (1 − p)⁴]

The exchange’s September 29 filing explicitly says the standard straight-trade formula remained unchanged.

For a single fill of 100 combo contracts at 50 cents, this September formula gives $1.8625, rounded to $1.86, rather than the standard $1.74. Unlike the standard formula, the combo curve is not symmetric around 50 cents.

Do not substitute the 0.06 extra-term coefficient shown in the later October-dated documentation into a September 25 calculation: the September filing specifies 0.04.

Rebates and rounding

The September taker rebate tiers were ordinarily based on prior-calendar-month taker volume:

• Below $250,000: no tiered rebate.
• $250,000 to less than $1 million: 10% of taker fees rebated.
• $1 million to less than $10 million: 25%.
• $10 million and above: 50%.

Those historical tiers are preserved in the redlined October taker-rebate amendment. An accelerated-placement exception allowed participants to provide verifiable proof of trailing-30-day trading volume on another prediction market and be assigned to the corresponding tier. That provision appears in the June 24 schedule.

The official fee documentation specifies weekly taker-rebate payouts, versus maker rebates applied at trade time. It defines taker volume as C × p for buys and C × (1 − p) for sells, not contract count multiplied by $1. Maker fills do not count.

The calculations above use nearest-cent, half-even rounding, as specified in the official documentation and recorded alongside the September coefficients in a September 24 marketcaster implementation update. The latter is an implementation record, not the exchange rule.

The documentation also describes a cumulative rounded-fee cap for an aggressive order split across fills, while maker rebates are calculated independently per fill. Multiplying an already-rounded one-contract fee by quantity can therefore give the wrong result.

What this changes about reading the odds

For a hypothetical contract paying $1 if YES wins and zero otherwise, buying 100 contracts at 50 cents in one standard taker fill costs $51.74 including the fee, before rebates or other charges. Under a risk-neutral, hold-to-settlement calculation, ignoring time value and resolution risk, that corresponds to a 51.74% break-even probability, not 50%.

That does not turn the quoted forecast into 51.74%. It separates the displayed price from the buyer’s economic threshold. Keep those numbers distinct when reading prices as probabilities or comparing all-in execution costs.

For trades after September, use the applicable dated schedule. October 2 filings specify further maker-rebate and taker-rebate amendments scheduled to take effect October 19, 2026. September’s coefficients and tiers should not be treated as permanent.