How to file Polymarket taxes

The customer agreement has you consent to electronic delivery of tax forms, Form 1099-B included, and the portfolio page offers no export. Each Polymarket US document and what it says on tax is on Polymarket tax forms.

So the filing figures come from the account’s own data, in the six steps below: four to gather and price it, one to reconcile it, and one to put it on the forms. What each export holds, field by field, is on Polymarket trade history.

The activity API, GET /v1/portfolio/activities, returns your trades, position resolutions, deposits, withdrawals, rebates and transfers. It needs an API key created at polymarket.us/developer; how that key works and what it can do is on Polymarket API key. Each item carries one of nine type names, which the schema describes only as a “Type of activity”. Sorting them by name is how Realize separates trading from cash:

A trade also has a state, and busted and rejected are among its values, so check it before counting a trade as a fill. Its cost basis and realized P&L can come back empty, and it has no fee field, so a trade on its own may lack its basis and always lacks the fee you paid. Steps 2 and 3 fill those in; the full field list is on Polymarket trade history.

An execution carries the commission the trade schema leaves out, and Polymarket US keeps executions for 7 days. Pull them on a schedule shorter than a week, since an execution not saved within that window is gone from this source; the changelog also records stored history being reset in three maintenance windows since. The retention dates in full are on Polymarket trade history.

For a week that was missed, the balance ledger in step 3 also carries fees, back to May 1, 2026.

The balance ledger, GET /v1/funding/balance-ledger/download, is a CSV of every cash balance change, fills and fees included. The reporting page lists CSV trade, execution, position and fee reports. Both serve nothing before May 1, 2026, and both are documented for the institutional API, so whether the key from step 1 reaches them is not stated.

A year that began before May 2026 has no CSV coverage for its first months, which leaves the activity API as the source for them.

Section 1256 treats a contract still open at the year end as sold at its fair market value, so for people filing that way every position held over December 31 needs a price for that day. The standard capital route reports a position only when it closes, and needs none. How the mark works is in the Section 1256 guide.

Polymarket US’s price history is public and keyed by the market’s slug, not its numeric id. Its Yes and No figures are display prices derived from the order book, not prices anything traded at, so a thin market can show a price no fill ever printed. Realize values a position open at the year end from this series at the end of the Eastern trading day, and leaves a market with no price that day off Form 6781 rather than mark it at a number it does not have.

A taker fee leaves your balance when the trade executes and a maker rebate is credited at the fill. Realize treats a resolution as the sale of whatever was still open, at the payout, matches lots first in, first out, and keeps the fee on each fill apart from price so each route can place it. The fee formula, rebate tiers and where fees appear in each download are on Polymarket fees.

When charged

Only when a trade executes: taker fees are deducted from the balance at the trade, maker rebates credited at the fill

Source

Settlement

No fee listed

Source

Taker rebate credits

ACTIVITY_TYPE_TAKER_FEE_REBATE in the activity API, from May 26, 2026; earlier shown as a referral bonus

Source

There is no IRS guidance on how event contracts are taxed. Of the people we’ve seen file, these are the most common ways they file, and each takes the same reconciled Polymarket US data in a different shape:

With no Form 1099-B behind the trades, the IRS’s own forms name where unreported transactions go: Form 8949 boxes C and F, and Form 6781 part I, which asks filers to list each one separately.

For people filing as standard capital gains, the lots go line by line onto Form 8949, as the capital gains guide shows. For people filing under Section 1256 because of the 60/40 split, the year’s total goes on Form 6781. For people filing as gambling, the gambling guide covers Schedule 1 and the itemized loss. A losing year under each route is in the losses guide.

Does Polymarket US give you a tax export or a P&L statement?

None is documented for retail accounts. The portfolio page describes your cash balance, open positions and total account value, and the reporting page lists CSV trade, execution, position and fee reports with no tax, 1099, cost basis or P&L content.

Will Polymarket US send me a 1099-B?

Its customer agreement has you consent to electronic delivery of all tax forms, including IRS Form 1099-B, but states no threshold, date or commitment to issue one, and no page of its documentation mentions a 1099. A year can be filed from your own trade data either way.

How far back can I get my Polymarket US data?

The CSV reports and the balance ledger serve nothing before May 1, 2026, and execution records are kept 7 days. For anything earlier, the activity API is the source for trades and position resolutions.

Why is costBasis empty on some of my Polymarket US trades?

The activity API’s schema marks a trade’s costBasis and realizedPnl as nullable, so either can come back empty. The basis of a lot can be rebuilt from the price and quantity of the trades that opened it.

Can I use the Polymarket US price history for December 31?

It is the public series Polymarket US publishes, keyed by market slug, but it is built from Yes and No display prices on the book, not from trades. Realize values a position open at the year end from it, and leaves a market with no price that day off Form 6781.

Do I report polymarket.com and Polymarket US the same way?

This walkthrough covers Polymarket US only, the CFTC-designated exchange run by QCX LLC that trades in US dollars. Polymarket’s own docs describe polymarket.com as a separate, crypto-based product, and its data comes from a different place.