Do you need tax software for Polymarket, or is a spreadsheet enough?

Honest answer first: if you made ten trades on two markets that both resolved, a spreadsheet is fine. Columns for market, outcome, qty, buy price, proceeds, dates — twenty minutes of work, no software needed. Anyone telling you that trader they need a $19 tool is selling something.

The failure modes start small and compound:

• Volume: a sports-bettor's season is hundreds of fills. Every merge, split, and resolution is a row; one missed merge and the basis is wrong everywhere downstream.
• FIFO lot-matching: selling 150 of 200 shares bought at two prices requires splitting the sale across lots by hand. Do that forty times without an error.
• Worthless positions: losers don't show up in any export you'd naturally keep — they're deductions you have to remember to record at $0.00.
• Unmatched transfers: shares moved in from another wallet have no visible acquisition; a spreadsheet happily assumes zero basis and inflates your gain.
• Country rules: UK pooling is average-cost, not FIFO; Germany splits at the one-year line. Formulas built for one regime quietly lie in another.

Ask two questions. One: how many dispositions? Under ~30, spreadsheet. Over ~100, error probability beats software cost. Two: what's the cost of being wrong? If an examination would mean reconstructing hundreds of lots from transaction hashes by hand, the $19 report that already carries the hash per row is cheap insurance.

The privacy angle matters too: the alternative to a spreadsheet isn't only manual work, it's often upload-SaaS — handing your complete betting history to a subscription service. Browser-side computation is the third option: the software does the math, and your history never leaves your tab.