How prediction markets resolve disputes

Most prediction markets resolve without fuss: the event happens, the source publishes the result, and winners are paid. But sometimes the outcome is unclear, the rules didn’t anticipate what happened, or traders disagree with the result. Polymarket and Kalshi handle those cases very differently. This guide explains both, from their documentation as checked in October 2026.

Polymarket: the UMA optimistic oracle

Polymarket’s main exchange uses UMA, a crypto oracle, to report outcomes. It’s “optimistic”: a proposed answer is assumed correct unless someone challenges it.

1. Proposal. Someone proposes the outcome and posts a bond, typically $750. Since September 2025 only whitelisted proposers with a strong track record can propose on Polymarket, though anyone can still dispute.
2. Challenge window. For two hours, anyone can dispute by posting an equal bond. If nobody does, the market resolves, roughly two hours after the proposal.
3. First dispute. The first challenge simply resets the process with a new proposal.
4. Second dispute. If the new proposal is also disputed, there’s a 24–48 hour debate period, with evidence posted in UMA’s Discord, followed by a vote of UMA token holders lasting about 48 hours.
5. Result. The winning side gets its bond back plus half the loser’s bond. A disputed market typically takes 4–6 days in total.

Possible outcomes include Yes, No, “too early” (the event hasn’t finished, so the process restarts later) and, rarely, 50-50, where each share redeems for 50¢.

Clarifications on Polymarket

If a market’s wording turns out to be ambiguous, Polymarket can add an “additional context” note, published on the blockchain. It can’t change the question’s basic intent, and UMA voters are expected to take it into account. Traders can request one in Polymarket’s Discord. Polymarket says it can’t alter or reverse a resolution once UMA has decided.

How to dispute on Polymarket

Use the link in the market’s Rules section, which takes you to UMA’s app, and post the dispute bond during the challenge window. If you’re wrong, you lose the bond, so disputing is for clear-cut errors, not for outcomes you dislike.

Polymarket US

The US app works differently: as a CFTC-regulated exchange, it decides outcomes itself using the sources named in each market’s rules. Its documentation says all resolutions are final, and its CFTC filings describe an internal outcome review process whose decisions aren’t subject to appeal.

Kalshi

• Who decides. Kalshi’s markets team determines the outcome from the source named in each market’s rules, such as a government agency, league or index provider.
• Flagging a market. If you think a market should already have settled, you can use “Request to settle” in the app.
• Outcome review. Kalshi’s rulebook provides for a formal market outcome review by a small committee including public directors, whose decision is final. Rulebook versions change, so check the current one for details.
• Unforeseen events. If an outcome can’t be determined as written, Kalshi’s rules allow settlement at a fair value such as the last traded price. In 2026 Kalshi applied this to a market about Iran’s leader after his death, reimbursed traders’ fees and net losses after a backlash, and then amended its rules to spell out how such cases settle.

How to avoid resolution surprises

• Read the rules, not the title. The rules name the source, the deadline and edge cases.
• Check the date and time zone. “By December 31” usually means a specific time in Eastern Time.
• Compare venues carefully. The same headline question can resolve differently on Polymarket and Kalshi. Our price-gap scanner only pairs markets we’ve checked ask the same thing.
• Be wary near the line. When an outcome hinges on a technicality, the price can stay away from $0 or $1 until resolution, and that’s a real risk.

FAQ

Related: How to sell or cash out early · Prediction market glossary · Kalshi vs Polymarket