Prediction Market
Arbitrage in 2026

Prediction markets on the same event can trade at different prices across platforms because they have separate liquidity pools and different trader bases. When a price difference creates a guaranteed profit after fees, that's an arbitrage opportunity.

This is pure arbitrage: the profit is independent of the outcome. The challenge is finding these windows before they close, executing both legs fast enough, and making sure fees don't erase the spread.

1. 1
   Maintain funded accounts on both platforms

   You need capital deployed on both platforms before you see an opportunity. An arb window often lasts minutes or less: transferring funds after you spot the discrepancy is too slow. Keep a float on Kalshi, Polymarket, and PredictIt simultaneously.

2. 2
   Monitor the same market on multiple platforms

   Check the same contract on each platform side by side. Tools: use each platform's web app in separate browser tabs, or build a simple script using Kalshi's REST API and Polymarket's CLOB API to compare prices automatically. Manual monitoring is feasible for 5–10 markets; systematic monitoring requires API work.

3. 3
   Calculate the arb after fees

   An apparent 5-cent discrepancy may not be profitable after fees. Kalshi charges 0–7% of profit on winning trades; PredictIt charges 10% of profit + 5% withdrawal. Calculate both legs: (price spread × position size) − (Kalshi fee on winning leg) − (PredictIt fee on winning leg). If the net is positive, it's profitable.

4. 4
   Execute both legs as simultaneously as possible

   Place both orders as close together in time as possible. The slower leg creates risk: if the market moves between the first and second trade, you may have a partially-hedged directional position rather than a pure arb. Limit orders on both platforms help; market orders are faster but may fill at worse prices.

5. 5
   Manage until resolution

   Hold both positions until the market resolves. Don't exit early: early exit introduces new execution risk. At resolution, one leg wins and one loses; your net profit is the price spread minus fees that you locked in at entry.

6. 6
   Track and report each platform separately for taxes

   Each platform issues its own 1099-MISC. Your Kalshi profits and PredictIt profits are reported separately. The arb may show a profit on one platform and an offsetting loss on the other: both are reportable. Work with a tax professional familiar with derivatives if you're doing this at volume.

Manual monitoring of 10+ markets across 3 platforms is unsustainable. Serious arb traders use the platforms' APIs to automate price monitoring and trigger alerts or orders:

To build a basic arb scanner: pull Kalshi and Polymarket prices for the same event (match by event title and resolution date), compare YES prices plus (1 − NO prices), flag any pair where the sum exceeds 1 + estimated fees, and alert for manual review or auto-execute. The hardest part is event matching: the same question is described differently on each platform.