01 · The rule
Combos use the ordinary taker formula.
Polymarket publishes one fee formula for the whole venue and does not list Combos separately:
Three things follow from it. The rate comes from the market’s category, and Combos are sports-only today, so 0.05 is the rate that applies. Only takers pay — accepting a quote makes you the taker, which is every Combo a normal user places. And the price in the formula is the Combo’s price, not the legs’.
02 · The consequence
The percentage is not a number. It is a curve.
Divide the fee by what the position cost you and the shares cancel, leaving feeRate × (1 − price). That is not a constant. It rises as the price falls, which means the more legs you stack, the closer the fee gets to the full rate.
| Combo price | Payout multiple | Fee, as a share of cost | As a share of total outlay |
|---|---|---|---|
| 45¢ | 2.2× | 2.75% | 2.68% |
| 30¢ | 3.3× | 3.50% | 3.38% |
| 20¢ | 5.0× | 4.00% | 3.85% |
| 10¢ | 10.0× | 4.50% | 4.31% |
| 5¢ | 20.0× | 4.75% | 4.53% |
| 2¢ | 50.0× | 4.90% | 4.67% |
A two-leg Combo and a ten-leg Combo are not charged at the same percentage, and the gap between the ends of that table is close to a factor of two. Any single “Combos cost X%” figure is one row of it being quoted as if it were the whole table.
03 · A distinction worth keeping
Two percentages, both correct.
The fee is charged on top of the position rather than taken out of it, so there are two honest denominators and they give different answers:
- Share of cost — the fee against what actually bought the position. This is feeRate × (1 − price), and it is the one that matches the formula directly.
- Share of outlay — the fee against the total debited from your balance. Slightly smaller, because the denominator includes the fee itself. This is the one that matches what the venue reports on a position you hold.
Worth knowing which you are reading. Somebody quoting a percentage off their own trade is almost always quoting the second; a calculator applying the formula is giving you the first.
04 · Verification
Checked against a position, not just a doc page.
A real 17-leg Combo reported a gross cost of $9.99982, of which $9.54 bought the position and $0.45982 was fee — 4.598% of the total debit.
Solving the published formula for the price that produces those three numbers at the sports rate gives a Combo price near 3.6¢, roughly a 28× payout — an ordinary place for 17 legs to land. The politics rate implies a negative price, and the crypto rate implies a multiple of about three on 17 legs. Neither fits; the sports rate does.
05 · Reference
The rate depends on the category.
Only the sports row is reachable through a Combo today. The rest are listed because the Combo catalog already carries markets from other categories waiting to be switched on — and because one of them charges nothing.
| Category | Taker rate | Combo-eligible today |
|---|---|---|
| crypto | 0.07 | No |
| sports | 0.05 | Yes |
| finance | 0.04 | No |
| politics | 0.04 | No |
| economics | 0.05 | No |
| culture | 0.05 | No |
| weather | 0.05 | No |
| other | 0.05 | No |
| mentions | 0.04 | No |
| tech | 0.04 | No |
| geopolitics | 0 | No |
Geopolitics is the row worth watching, because its taker rate is zero: a Combo built only from geopolitics legs would carry no venue fee at all. Polymarket has said it will enable geopolitics markets above $500,000 in volume, and the catalog already carries 158 such markets staged and switched off — every one of them above that volume line. Staged is not tradable, and Polymarket has not published a date, so this page will say they are live when the catalog says so and not before.