Do you pay taxes on Polymarket profits?

Yes. Polymarket profits are taxable in the US even though Polymarket does not issue tax forms. Profits are likely treated as short-term capital gains on crypto property transactions. Each trade where you sell shares for more than you paid creates a taxable event. You are responsible for tracking cost basis and reporting all gains on your tax return. If you trade frequently, consider using a crypto tax tool like CoinLedger or Koinly to track transactions.