Tax-Loss Harvesting on Polymarket and Kalshi Before December 31

Selling a losing Polymarket or Kalshi position before December 31 can lock in a loss that offsets your 2026 gains, but this helps mainly if you report under capital treatment. There it offsets gains in full, plus up to $3,000 of other income. Under gambling treatment it can actually add little or nothing, and under other-income treatment it only matters by reducing your net. Harvesting also costs real money in spread and fees, so check the numbers before you sell.

OddsFile is software, not tax advice. The IRS has not issued guidance on how prediction-market contracts are taxed. This article explains the options and the sources behind them; a tax professional can tell you which position fits your situation.

Harvesting by treatment

Stick with one treatment. Using capital treatment for your losses and something else for your gains in the same year isn't a defensible approach. See gambling vs capital gains.

Worked example

You have $9,000 of realized short-term gains in 2026 and are in the 24% bracket. You still hold a Kalshi position that cost $4,000 and could sell for $1,000 today.

Against that $720, count your costs. If the spread and fees cost $40 to exit, the net benefit is $680. You also give up whatever the position might have been worth at resolution. If you think it's worth more than $1,000, you're selling a good bet for a tax timing benefit.

Note what harvesting really does: it moves a loss into this year. If the position would lose anyway in 2027, you'd get the loss then, against 2027 gains. Harvesting pays most when you have gains this year and may not have them next year, or when the alternative is a tax rate that's lower next year.

Check first: losses you already have

Before selling anything, make sure you have counted what's already realized.

• Resolved losers you never redeemed. These are losses even though nothing moved on-chain, which makes them easy to miss. See unredeemed losing positions.
• Worthless shares in markets that resolved earlier in the year. There's nothing to sell, so don't try.
• Fees. They're already built into your basis and proceeds.

Many traders find they need to harvest less than they thought, or nothing at all.

Open positions: what's taxed and what isn't

Under capital, other-income and gambling treatment, an open position isn't taxed until it closes. A contract you hold through December 31 has no 2026 result, whichever way its price moved. For the full picture, see do you owe tax on open positions?

That also works in reverse. If you're sitting on winners, you can leave them open into January to defer the gain to 2027, as long as the market doesn't resolve first.

Year-end mechanics

Timing. Leave a margin. Polymarket records transactions on-chain with UTC timestamps, so a trade at 8 p.m. Eastern on December 31 is already January 1 in UTC. The date for your tax year is arguably your local date, but your software might use UTC. Avoid the last hours of the year.

Liquidity. Holiday order books are thin. On a long-shot market, the bid may be fractions of a cent, or nonexistent. A position with no buyer can't be harvested. You wait for resolution.

Near-worthless shares. Selling at a cent does create a clean disposal, as noted in unredeemed losing positions, but only if a buyer exists and the fee doesn't eat the benefit.

Rebuying. Under current law the wash sale rule probably doesn't apply, but the loss must still be bona fide. A pending bill could also change the result for Polymarket tokens for sales after September 14, 2026, if it becomes law as introduced. If you want the exposure back, leave a real gap and accept the risk.

The $3,000 limit and carryforwards

Capital losses offset capital gains without limit. Beyond that, you can deduct up to $3,000 a year against other income, or $1,500 if married filing separately, and carry the rest forward. A trader with no gains who harvests $20,000 gets a $3,000 deduction this year and carries $17,000 forward.

If you're already over the limit with no gains, more harvesting doesn't help you this year. It only adds to the carryforward.

Should you realize gains instead?

If your 2026 income is unusually low, or you already have a big capital loss, consider the opposite: closing winners in December rather than January. Capital losses you've already got can absorb the gains. It's the same logic in reverse.

A December checklist

1. Export your realized 2026 results from every venue and wallet.
2. Settle resolved losers on paper.
3. Note your net gain or loss, and which treatment you'll use.
4. List open positions below cost, with current bid, size and fee.
5. Compute tax saved minus exit cost.
6. Sell only what clears that bar, and do it by mid-December.
7. Write down what you did and why.

Run the free OddsFile check: paste a Polymarket or Hyperliquid address and see your 2026 P&L under each treatment, including unredeemed Polymarket losers, no signup. Then turn the result into a payment plan with estimated taxes.

FAQ

Does the sale date or the settlement date count?

Use the date your position closed. On Polymarket the trade settles on-chain. On Kalshi, use the fill date on your history and compare it with your annual statement.

Can I harvest a loss on a market that already resolved?

It's already a loss. The question is only whether you've recorded it in the right year.

Can harvested losses offset my stock gains?

Under capital treatment, yes. All capital gains and losses net together on Schedule D.

Do harvested losses help if I take the standard deduction?

Under capital treatment, yes. Capital losses don't require itemizing. Under gambling treatment, no.