Arbitrage

Also called arb · lock

Buying both sides of the same question at a combined all-in cost below the guaranteed payout, so every outcome pays.

The cross-venue form is the cleanest to state: buy N contracts of YES where it is cheaper and N contracts of NO on the other venue, so that whichever way the event resolves, exactly N dollars come back. The splitter prices both possible direction assignments, charges each leg its own fee, takes the cheaper, and treats the structure as viable only when the all-in cost per dollar of guaranteed payout is below 0.999.

A worked example from the arbitrage guide: Polymarket YES at 40¢ plus about 0.2¢ of gas and slippage, against Kalshi NO at 55¢ plus 1.7¢ of fee, is about 96.9¢ spent for a dollar that arrives either way.

Two things make real arbitrage far rarer than screens suggest. Fees ride on every leg and are heaviest near 50¢, which is exactly where price disagreements are most common, so the one and two cent gaps you will see most often clear nothing. And the two legs must be the same question — where resolution rules can diverge, the pair is marked as not lockable and rendered as a price signal with no stake split at all. An arb across mismatched rules is not an arb; it is an uncovered position you have been told is safe.

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Definitions describe how Polymarket and Kalshi behave and how WhaleTracks models them; venue rules and fee schedules can change, so confirm anything you size a position on with the venue itself. WhaleTracks is informational analytics, not financial advice. Past performance does not guarantee future results.