The same event often trades on Kalshi and Polymarket at different prices. Here's what those differences actually mean — wording, resolution source, and payout scope explained.
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Apr 2026
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The key takeaway from this page
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Three dimensions explain almost every cross-platform price gap.
Prediction markets are legal contracts. Every word in the title changes what the contract covers. 'Will X happen?' and 'Will X happen by [specific date] via [specific mechanism]?' are fundamentally different questions — and different settlement triggers.
Example
"Will the Fed cut rates?" captures any cut of any size at any meeting. "Will the Fed cut 25bp at the June 19 meeting?" captures exactly one scenario. A 50bp cut on June 19 resolves the first YES and the second NO.
Two contracts on the same event can use different data sources — and those sources can disagree. Official government data (NOAA, BLS, FOMC statements) tends to be more conservative and slower to update than consumer-facing data (Weather.com, CoinGecko).
Example
On a 95°F day in NYC, NOAA's official Central Park ASOS station might read 93.8°F (shaded, standardized placement). Weather.com might show 96°F. One contract resolves YES; the other NO — on the exact same day.
Scope changes the implied probability of YES. A broader question ('any cut, any size') will almost always be priced higher than a narrower question ('exactly 25bp cut'). This is not a mispricing — it is the market correctly pricing two different outcomes.
Example
If the Fed has a 70% chance of cutting at all, and a 50% chance of cutting by exactly 25bp (rather than 50bp), a 'any cut' contract should trade near 70¢ and a '25bp exactly' contract near 50¢. The 20¢ gap is not arbitrage — it reflects real probability difference.
Most cross-platform price gaps have a structural explanation. Four common reasons:
Different scope
Kalshi: any cut, any size. Polymarket: specifically 25bp. A 50bp surprise resolves YES on Kalshi, NO on Polymarket.
Different deadline
One contract expires March 31; the other April 30. Same event, different windows — both can be YES or NO independently.
Different resolution source
NOAA ASOS official station vs Weather.com reading. Same hot day, 2°F difference, one resolves YES, one resolves NO.
Actual arbitrage
Real — but closes within seconds to minutes on liquid markets. If you see it, it is almost certainly already gone.
Platform-specific contract mechanics
Binary event contracts on a central limit order book. Contracts pay $1 or $0. Resolution uses official data sources (BLS, NOAA, AP). Broadest category coverage — 9+ categories including weather, science, and entertainment. Fee: trading fee (charged when you buy at market price) — many markets are free.
In plain English: Kalshi's fee varies by odds — max 1.75¢/contract at 50/50. Near-certainties and longshots cost almost nothing.
Binary outcome tokens on Polygon blockchain. Trades via CLOB (Conditional Token Framework). US version resolves via centralized Markets Team under CFTC oversight; international version uses UMA optimistic oracle with on-chain dispute. USDC-denominated.
CFTC DCM + DCO. Binary contracts integrated into IBKR's institutional trading platform. Covers economics, politics, and finance — no sports. Contracts trade alongside stocks, options, and futures in the same IBKR account. Resolution uses official government and financial data sources.
Even when two exchanges list the same event, contract wording, resolution sources, and settlement timing may differ. Always read the full contract specification before assuming cross-platform prices are comparable.
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