Polymarket taxes in 2026: the 1099-DA guide

If you traded on Polymarket in 2026, you almost certainly have taxable events. Selling shares, merging a complementary pair, and redeeming a resolved position are all dispositions. Winning is not a windfall that arrives tax-free — it's the sale of an asset at $1.00. And starting with the 2026 tax year, brokers report digital-asset dispositions on the new Form 1099-DA, which makes accurate self-tracked basis more important than ever.

Every outcome token on Polymarket is its own asset. That means:

• Buying shares — not taxable by itself, but it sets your cost basis.
• Selling shares — a disposition. Proceeds are what you received; gain or loss is proceeds minus basis.
• A winning market resolving — a disposition at $1.00 per share, even if you never clicked redeem.
• A losing market resolving — a disposition at $0.00, and your full basis becomes a capital loss. Losing positions are deductions you only get if you track them.
• Merging a complementary Yes/No pair — a disposition at $1.00 per pair.
• Liquidity rewards — typically ordinary income at the USDC value received.

Form 1099-DA is the new broker report for digital-asset dispositions. It doesn't create new tax rules; it creates a paper trail. The catch for Polymarket traders is that the platform is not a US broker and doesn't send you a complete 1099 covering all activity — so the IRS may see a partial picture while your real basis lives in your own records. When a broker's numbers and yours disagree, your contemporaneous records are what you file from.

Practically: keep your fills, dates, and amounts. That's exactly what Bitfork Tax reads from Polymarket's public API and turns into a Form 8949-style export — computed entirely in your browser, with nothing uploaded to anyone.

For each disposition you want: acquisition date, disposal date, quantity, proceeds, cost basis, and the transaction hash. For rewards: the date and USDC value received. Keep the raw export alongside your summary — the hash column in a Bitfork Tax CSV points straight back to the chain for any line an examiner questions.