Prediction market arbitrage: the complete guide

Prediction market arbitrage is buying YES on an event at one venue and NO on the same event at another, so the pair costs less than the $1.00 it must pay out. When both markets resolve on identical terms, exactly one leg pays — whichever way the event goes.

How the YES + NO hedge works

Every binary prediction market contract settles at $1.00 (event happens → YES pays; doesn't → NO pays). If "Will X happen?" trades at YES $0.47 on Polymarket while the same question's NO costs $0.505 on Kalshi, the pair costs $0.975 and pays $1.00 either way — a 2.5% gross edge before fees. Nothing about the outcome matters; only that both venues resolve the same question the same way.

Why do prediction markets disagree?

Because the market is fragmented. Polymarket, Kalshi, PredictIt, Smarkets and Limitless serve different jurisdictions, currencies and user bases — a US-regulated exchange, an offshore crypto book and a UK betting exchange each attract different flows, and capital can't move freely between them (KYC walls, geo-restrictions, on/off-ramps). Prices drift apart faster than the small arbitrage community can pull them back together.

How big are real edges?

Smaller than the marketing you'll see elsewhere. On a live board of 40–70 detected pairs, most gross spreads sit between 0.5% and 3%; anything above ~10% is almost always a mismatched pair, a stale quote, or a market you can't actually trade. Annualized returns depend heavily on time-to-resolution — a 2% edge that locks capital for two years is a worse deal than a T-bill.

The risks that eat naive arbitrage

The math is the easy part. The losses come from everything around it:

• Resolution mismatch — "similar wording" is not "same market." Win vs nomination, first-round vs runoff, different price indexes or deadlines: if the two markets can resolve differently, both legs can lose. This is the #1 killer.
• Fees — Kalshi charges a taker fee, PredictIt takes 10% of winning-side profit; a 2% gross edge can be sub-1% net.
• Depth — the displayed price may hold for 20 contracts, not 2,000. Walk the order book before sizing.
• Jurisdiction — Kalshi and PredictIt are US-only; Polymarket restricts US persons; Smarkets is UK/EU. Many pairs cannot legally be held by one person.
• Capital lock-up — your money is parked until resolution, which can be years for election markets.
• Taxes — winnings on one venue may be taxable without netting the other venue's losing leg.

Is prediction market arbitrage risk-free?

No. It's a modeled edge that becomes real only if both markets resolve on identical rules, your orders fill at the displayed prices, and the after-fee, after-tax math still clears. Treat every "guaranteed profit" claim as a red flag — including ours, which is why we don't make one.

How to find opportunities

Manually: watch the same events across five venues and compare order books — practically impossible at scale. In practice you need a scanner that matches the same real-world event across venues, prices both hedge directions net of each venue's fees, and verifies live depth. That is exactly what PROVISUM does, every 10 minutes.

Keep reading: Polymarket vs Kalshi: fees, access & price gaps · Polymarket arbitrage: finding mispriced markets