How prediction markets resolve: Kalshi vs Polymarket settlement
Kalshi and Polymarket US settle markets centrally: the exchange applies its CFTC-filed rules and named data sources, and its decision is final. Polymarket.com, the international site, uses the UMA optimistic oracle. Anyone can propose an outcome by posting a bond of about $750, and disputes go to a vote of UMA token holders.
That difference matters most in the edge cases, which is where traders lose money they thought they had won.
Kalshi: rulebook, source agency, review committee
Kalshi (KalshiEX LLC) is a designated contract market regulated by the CFTC. Each market has contract terms filed with the CFTC. They name a Source Agency, which the rulebook defines as "the agency that publishes the Underlying and/or Expiration Value." Examples include an official statistic, a league result or a price index.
The rulebook defines the outcome mechanically. If the Expiration Value falls within the Payout Criterion, the market resolves Yes, otherwise No. A Yes contract then pays $1 and a No contract pays $0, or the reverse. Kalshi's developer docs say markets "typically settle shortly after expiration," with timing that depends on the data source and any manual review.
When the answer is unclear, the rulebook (version 1.15, the copy we reviewed) gives Kalshi two tools:
- Last traded price. Under Rule 6.3, if it cannot be determined whether the outcome was met, Kalshi "may use the last traded price of the Contract to determine the payout."
- Outcome Review Committee. If there is no usable last price, or Kalshi decides it is not a fair settlement, this committee makes a binding allocation. It has three members appointed by the Regulatory Oversight Committee, at least two of them Public Directors. Its determinations are "final and not subject to review."
Polymarket.com: the UMA optimistic oracle
Polymarket.com is not a US-regulated exchange, and it is close-only for US users. Its markets resolve onchain:
- Proposal. Anyone proposes the outcome and posts a bond, typically about $750. A wrong or early proposal forfeits the bond.
- Challenge window. For 2 hours, anyone can dispute by posting a matching bond. With no dispute, the market resolves.
- Second round. A first dispute triggers a new proposal. If that one is disputed too, there is a 24 to 48 hour debate period.
- DVM vote. UMA token holders vote for about 48 hours. The result can be Yes, No, "too early," or, rarely, 50/50, where each token redeems for $0.50.
Polymarket's docs put an undisputed resolution at about 2 hours and a disputed one at about 4 to 6 days. Polymarket can also post "Additional context" clarifications after trading starts. Its docs say clarifications cannot change a question's core intent.
Polymarket US: exchange-determined settlement
Polymarket US (QCX LLC) is a separate CFTC-designated contract market with its own rulebook. It does not use UMA. In a contract filing with the CFTC dated October 20, 2026, QCX states that the exchange is the Source Agency, names the primary data source, and describes a Contract Outcome Review Process (Rule 10.4) for data errors or unclear results. Once the exchange determines an outcome under the contract's criteria, the filing says it is final "and is not subject to appeal or revision." That filing covers a crypto price contract. Terms for other markets are filed separately, so read the rules on the specific market.
Side by side
| Kalshi | Polymarket US | Polymarket.com | |
|---|---|---|---|
| Regulator | CFTC (DCM) | CFTC (DCM) | Not US-regulated |
| Who decides | Exchange, under filed terms | Exchange, under filed terms | UMA oracle and token-holder vote |
| Unclear outcome | Last traded price or Outcome Review Committee | Contract Outcome Review Process | Dispute, DVM vote, possible 50/50 |
| Typical time | Shortly after expiration | No later than the day after expiration, unless reviewed (per the filing) | About 2 hours; 4 to 6 days if disputed |
| Appeal | Committee decisions are final | Outcome final once determined | DVM vote is final |
Resolutions that went wrong or split
Ukraine mineral deal, March 2025 (Polymarket.com). "Ukraine agrees to Trump mineral deal before April?" jumped from 9% to 100% between March 24 and 25 and resolved Yes, though Ukraine had not agreed to the deal. Users alleged a large UMA holder swung the vote. Polymarket called it "an unprecedented situation" and said it would not issue refunds, according to The Block.
Zelenskyy suit, July 2025 (Polymarket.com). A market with more than $237 million in volume asked whether Zelenskyy would be photographed in a suit by June 30. He wore a black jacket and matching trousers at a NATO event on June 24, which many outlets called a suit. The UMA process finalized No, citing insufficient consensus in credible reporting, per Decrypt.
Cardi B halftime show, February 2026 (both). Kalshi's terms did not count appearing on stage without singing or playing as a performance. With the facts unclear, Kalshi settled at the last traded price, 26¢ Yes and 74¢ No. Polymarket's UMA-resolved market settled Yes. A Kalshi Yes holder filed a CFTC complaint seeking $3,700, per the AP.
Khamenei markets, February 2026 (Kalshi). After US and Israeli strikes on Iran on February 28, Kalshi halted and then settled its "Khamenei out" markets, citing its policy of not offering markets that settle on death. The CFTC-filed terms referred to the last price "prior to the death," while the market page said "prior to confirmed reporting of death." Kalshi called its language "grammatically ambiguous" and reimbursed some users, per DeFi Rate.
How to protect yourself
- Read the full rules, not the market title. Find the source, the deadline and the edge-case clause.
- Treat a vague word ("perform," "suit," "agree") as a risk you are pricing.
- If you hold the same question on two venues, assume they may settle differently. Our arbitrage guide works through what that does to a hedged pair.
Before you trade, compare the same market across venues on our live comparison. For the basics of contracts and payouts, see how prediction markets work.
FAQ
Who decides the outcome of a Kalshi market?
Kalshi does, by applying the contract terms it filed with the CFTC and the named Source Agency. If the outcome cannot be determined, its rulebook lets it settle at the last traded price or send the question to its Outcome Review Committee, whose decision is final.
Does Polymarket US use the UMA oracle?
No. Polymarket US (QCX LLC) is a CFTC-regulated exchange that determines outcomes under its own rulebook and filed contract terms. UMA is used by the international Polymarket.com site.
How long does a Polymarket dispute take?
On Polymarket.com, an undisputed proposal resolves after a 2-hour challenge window. Polymarket's docs say a disputed market that goes to a UMA vote takes about 4 to 6 days.
Can a prediction market settle at something other than $1 or $0?
Yes. Kalshi can settle at the last traded price when the outcome is unclear, as it did at 26¢/74¢ in the February 2026 Cardi B market. Polymarket.com can resolve a market 50/50.