How to export your trade history from Kalshi and Polymarket US
Why the export matters
With no 1099-B in the pipeline, your trade history is the only complete record of what you bought, sold, and paid in fees. Tax software, accountants, and DIY spreadsheets all start from this file. Venues are under no obligation to keep deep history available in the account interface forever — export before you need it.
Kalshi
Kalshi exposes trade history in the account interface (the portfolio/activity section) and through its API for programmatic access. The export includes fills with timestamps, prices, quantities, and fees — the fields every gain/loss computation needs.
Export at least quarterly, and monthly if you trade actively. Keep the raw files unchanged; do any cleaning in copies.
Polymarket US (QCX)
QCX accounts expose positions and statements through the account dashboard. The exchange is young and its reporting surface is still evolving, which cuts both ways: expect the export options to improve, and do not rely on any particular view existing next year.
Save statements as they are issued and screenshot account summaries at year-end. A dated artifact beats a memory in any reconstruction.
What to do with the files
Store exports somewhere durable and boring — a cloud folder with version history is fine. When tax season arrives, the computation is mechanical: match buys and sells (FIFO is the default assumption), subtract fees, and total by venue. Tools that automate this are emerging; none is yet the default answer.
FAQ
How far back can I export Kalshi trade history?
The account interface and API expose substantial history, but the venue does not guarantee permanent availability. Export on a schedule rather than assuming you can reconstruct later.
Does the export include fees?
Kalshi's fill-level records include fees, and fees are part of your cost basis and proceeds for tax purposes. Keep the raw export so the fee column survives.
Is a screenshot of my P&L enough for taxes?
No. Summary P&L views are not a filing-grade record. You need trade-level data: timestamp, contract, side, price, quantity, and fee per fill.