Short version: Polymarket charges zero protocol trading fee. You trade USDC shares against the order book directly. Real costs are USDC bridging (one-time), Polygon gas (cents per trade), and spread in low-liquidity markets.
Worked example: 100 shares at 50¢
You buy 100 YES shares at 50¢. Notional: $50.00. Polygon gas: ~$0.02. Bid/ask spread on a deep market like the Super Bowl winner: roughly $0.01 round-trip per share at 50¢ pricing. You exit at 60¢ — another ~$0.02 gas. Net profit: $10.00 minus ~$0.05 in costs = $9.95. For active traders, this is materially cheaper than Kalshi's per-trade fee schedule.
Polymarket vs Kalshi fees
| Cost | Polymarket | Kalshi |
|---|---|---|
| Trading fee | 0% protocol | Scaled, peak ~0.7% one-way |
| Deposit | USDC bridging + ramp fees | ACH free · debit small fee |
| Withdrawal | USDC network fees | Free ACH |
| Tax doc | Self-report | 1099 issued |
When Polymarket wins on cost
- High-volume traders — 0% × big size beats 0.7% × big size every time.
- Deep liquid markets — penny spreads erase the spread disadvantage.
- Holding to resolution — no exit cost at all.
When Kalshi wins on cost
- One-off small trades — bridging fees overwhelm a $20 deposit on Polymarket.
- Niche or new markets — wider spreads on Polymarket cost more than Kalshi's fee.
- Tax simplicity — Kalshi's 1099 is worth real money in CPA time.
Sources & references
More: Polymarket taxes (Texas) · How to use Polymarket · Kalshi fees compared