A prediction market resolves when an exchange or its designated oracle confirms the outcome against a source named in the market's rules, paying $1 or $0 for each contract.1Kalshi Help Center, "Market FAQs," help.kalshi.com, April 20262Polymarket Documentation, "Resolution," docs.polymarket.com, accessed October 2026
Whether a trade pays out depends on who holds resolving power and what information sources they are required to check.3Kalshi Help Center, "Market FAQs," help.kalshi.com, April 2026 Kalshi and Polymarket use two distinct models to answer that question.4Kalshi Help Center, "Market FAQs," help.kalshi.com, April 20265Polymarket Documentation, "Resolution," docs.polymarket.com, accessed October 2026
Where is a prediction market's resolution source written?
A market's resolution source is written directly in its contract rules before trading opens, and rules can specify a single source or several acceptable outlets.6Kalshi, "What will Trump say?" series settlement sources (KXTRUMPMENTION; event "What will Trump say during the United Nations General Assembly?"), Kalshi public API, accessed October 20267Kalshi Help Center, "Market FAQs," help.kalshi.com, April 20268Polymarket Help Center, "How are markets clarified?," help.polymarket.com, June 2026 Polymarket states in its help center: "The rules specify the resolution source, the market end date, and they outline how the market should resolve in various edge-cases".9Polymarket Help Center, "How are markets clarified?," help.polymarket.com, June 2026
On Kalshi, each market lists its settlement sources in its rules; for example, a market on a presidential address named 14 acceptable outlets, including the Associated Press, Reuters, CNN and The Wall Street Journal.10Kalshi, "What will Trump say?" series settlement sources (KXTRUMPMENTION; event "What will Trump say during the United Nations General Assembly?"), Kalshi public API, accessed October 2026
Exchanges establish these sources before any trades occur.11Kalshi Help Center, "Market FAQs," help.kalshi.com, April 2026 Kalshi's help center notes that markets rely on a "source agency" such as official league statistics, government releases, or other event authorities to publish finalized results.12Kalshi Help Center, "Market FAQs," help.kalshi.com, April 2026 If none of the sources listed in the rules report the outcome, the contract does not count it.13Gambling911, "Kalshi Resolves Bernie Sanders Greensboro Rally Mentions as 'No' Despite Reports He Said These Things," gambling911.com, February 2026
How does Kalshi decide the outcome?
Kalshi resolves outcomes through internal staff checks and a board review committee.
- Market close: Trading ends at the scheduled time, or immediately when an outcome occurs.14Kalshi Help Center, "Market FAQs," help.kalshi.com, April 2026
- Staff verify against source agencies: Most markets settle within a few hours after the outcome is known, often within about three hours.15Kalshi Help Center, "Market FAQs," help.kalshi.com, April 2026 Each contract contains a predefined settlement timer specifying when payouts finalize after a determination is reached.16Kalshi API Documentation, "Get Market," docs.kalshi.com, accessed October 2026
- Outcome Review Committee evaluation: Kalshi can route the market to a three-member committee (including at least two public directors) that must issue a final decision within 24 hours.17KalshiEX LLC, "Rulebook, Version 1.29" (Rules 2.7, 6.3, 7.1, 7.2 and Chapter 10), kalshi-public-docs.s3.amazonaws.com, 2026
Further, if contract rules cannot determine an outcome, Kalshi may settle the market at the last traded price or defer the ruling to the committee (Rule 6.3(c)).18KalshiEX LLC, "Rulebook, Version 1.29" (Rules 2.7, 6.3, 7.1, 7.2 and Chapter 10), kalshi-public-docs.s3.amazonaws.com, 2026 If a designated source agency stops publishing or undergoes significant changes, Kalshi reserves the right to designate a substitute source (Rule 7.2).19KalshiEX LLC, "Rulebook, Version 1.29" (Rules 2.7, 6.3, 7.1, 7.2 and Chapter 10), kalshi-public-docs.s3.amazonaws.com, 2026
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How does Polymarket decide the outcome?
Polymarket's international platform settles outcomes through a decentralized proposal and dispute system powered by the UMA Optimistic Oracle.
- Proposal: A whitelisted address submits the proposed outcome along with a collateral bond.20Polymarket Documentation, "Resolution," docs.polymarket.com, accessed October 202621The Block (Danny Park), "UMA's oracle update to limit Polymarket resolution proposals to whitelisted parties to improve market outcomes," theblock.co, August 2025 The initial whitelist of 37 addresses included Risk Labs and Polymarket employees.22The Block (Danny Park), "UMA's oracle update to limit Polymarket resolution proposals to whitelisted parties to improve market outcomes," theblock.co, August 2025
- Challenge window: A two-hour window opens upon proposal submission. Any market participant can challenge the proposed outcome during this window by posting a matching bond. Undisputed proposals finalize automatically when the window closes.23Polymarket Documentation, "Resolution," docs.polymarket.com, accessed October 202624Polymarket Help Center, "How are markets disputed?," help.polymarket.com, April 2026
- Debate and vote: If a proposal is disputed twice, the issue escalates to UMA token holders, who vote to select the winning outcome.25Polymarket Documentation, "Resolution," docs.polymarket.com, accessed October 202626Polymarket Help Center, "How are markets disputed?," help.polymarket.com, April 202627Decrypt (Sebastian Sinclair), "Polymarket Rules 'No' on $237M Controversial Bet Over Zelenskyy's Suit," decrypt.co, July 2025 Disputed resolutions typically take four to six days to fully resolve.28Polymarket Documentation, "Resolution," docs.polymarket.com, accessed October 2026
Polymarket US, the CFTC-regulated exchange, operates differently. Rather than using decentralized oracle votes, Polymarket US functions like Kalshi, relying on centralized internal authority to review outcomes under its own rulebook, where determinations made by the exchange are final.29Polymarket US, "Polymarket US Rulebook" (Rule 10.4 and Chapter 9), polymarketexchange.com, March 2026
Can a resolution be reversed?
Resolutions generally cannot be reversed once an exchange or oracle finalizes the outcome.30KalshiEX LLC, "Rulebook, Version 1.29" (Rules 2.7, 6.3, 7.1, 7.2 and Chapter 10), kalshi-public-docs.s3.amazonaws.com, 202631Polymarket Help Center, "How are markets disputed?," help.polymarket.com, April 2026 Polymarket notes in its help documentation: "Polymarket is non-custodial and cannot alter or reverse market resolutions. Once finalized by UMA, outcomes are immutable".32Polymarket Help Center, "How are markets disputed?," help.polymarket.com, April 2026 Following the contested $7 million Ukraine minerals market, Polymarket declined user requests for refunds: "because this wasn't a market failure, we are not able to issue refunds".33crypto.news (Trisha Husada), "Polymarket suffers governance attack due to UMA whale intervention," crypto.news, March 2025
Exchanges operating under US jurisdiction rely on formal legal frameworks rather than blockchain immutability.34KalshiEX LLC, "Rulebook, Version 1.29" (Rules 2.7, 6.3, 7.1, 7.2 and Chapter 10), kalshi-public-docs.s3.amazonaws.com, 202635Polymarket US, "Polymarket US Rulebook" (Rule 10.4 and Chapter 9), polymarketexchange.com, March 2026 On Kalshi, the Outcome Review Committee's determinations are final.36KalshiEX LLC, "Rulebook, Version 1.29" (Rules 2.7, 6.3, 7.1, 7.2 and Chapter 10), kalshi-public-docs.s3.amazonaws.com, 2026 A participant can elect to take a claim against another participant arising from a Kalshi contract to arbitration under Chapter 10 of its DCM rulebook.37KalshiEX LLC, "Rulebook, Version 1.29" (Rules 2.7, 6.3, 7.1, 7.2 and Chapter 10), kalshi-public-docs.s3.amazonaws.com, 2026
Similarly, participant disputes on Polymarket US proceed to binding arbitration in New York under Chapter 9 of its rulebook.38Polymarket US, "Polymarket US Rulebook" (Rule 10.4 and Chapter 9), polymarketexchange.com, March 2026 A market's rules and resolution sources are set before trading starts.39Kalshi Help Center, "Market FAQs," help.kalshi.com, April 202640Polymarket Help Center, "How are markets clarified?," help.polymarket.com, June 2026