Polymarket, on the record.

On October 8, 2026, none of the 322 pages in the Polymarket US documentation mentioned a 1099, a W-9 or the IRS, and its help pages have no tax section.

The one primary document that names a form is the participant agreement, in which you consent to the electronic delivery of “all tax forms, including, without limitation, IRS Form 1099-B”. That sets how a form would be delivered. It does not say that one will be sent, or what it would show.

Polymarket US collects a Social Security Number at signup, and its identity checks come before any deposit or trade. Gross income includes gains “from whatever source derived” (IRC §61), whether or not a form reports them, so with or without a form, the figure for a Polymarket US year is built from the trade record.

The fee schedule, effective from 10 AM ET on October 7, 2026, charges a taker 0.0695 x C x p x (1 - p), where C is the number of contracts and p the price, and 0.10 x C x p x (1 - p) in table tennis markets. The standard fee peaks at 50¢, at $1.74 per 100 contracts ($2.50 in table tennis). A resting order is paid a rebate of 0.0125 x C x p x (1 - p), which peaks at $0.31 per 100 contracts at 50¢; combo fills carry no maker rebate. Fees and rebates are rounded to the nearest cent by banker’s rounding (round half to even), and apply only when a trade executes.

The schedule lists no fee at settlement, and the funding page lists no fee for deposits by debit card, ACH, Apple Pay, PayPal, Venmo, USDC where available, or wire, and none for withdrawals. Takers with more than $250,000, $1 million or $10 million of taker volume in the prior month get back 10%, 25% or 50% of their taker fees.

Two filings dated October 2, 2026 would change the rebates, each effective ten business days after certification: no maker rebate under $10 million of prior-month maker volume, tiered above it, and taker volume rebates of 3%, 5%, 10%, 15% or 30% in tiers starting at $250,000, $1 million, $10 million, $25 million and $50 million a month. Kalshi vs Polymarket puts both exchanges’ fee formulas side by side, with a calculator for any price and size.

The Polymarket US documentation describes no export for app users: the portfolio page shows cash, open positions and account value. Your history is served by the activity API, GET /v1/portfolio/activities, which returns trades, position resolutions, deposits, withdrawals, rebates and transfers. Each trade carries its price, quantity, whether it was the aggressor, cost basis and realized P&L; the published schema has no fee field.

API keys are Ed25519, created at polymarket.us/developer after identity checks, and the authentication docs describe no read-only scope. The CSV reports in the reporting guide are documented for the institutional API, with a historical floor of May 1, 2026. The changelog says execution records are kept for 7 days from July 16, 2026, and that the pruning left trades and positions unchanged.

Polymarket US publishes price history keyed by market slug. Its prices are book-derived Yes and No display prices, not trades. Realize connects to Polymarket US with an API key you create on the exchange, reads your trades with it, and its client implements no order endpoint, so it cannot place a trade.

There is no IRS guidance on how event contracts are taxed. Of the people we’ve seen file, three routes are the most common: standard capital on Form 8949 and Schedule D, Section 1256 on Form 6781, and gambling, with winnings on Schedule 1. Each works the same way for a Polymarket US trade as for a Kalshi trade.

For people who file under Section 1256 because of the 60/40 split, the exchange matters to that reading: they point to §1256(g)(7)(B), which counts as a qualified board or exchange “a domestic board of trade designated as a contract market by the Commodity Futures Trading Commission”. That designation belongs to Polymarket US, not to polymarket.com. Prediction market taxes prices the three routes on one year, and the Polymarket US tax calculator gives a federal range for your own net.