Short answer: we found no evidence that Polymarket or Kalshi cap or close accounts because they are profitable. That is different from sportsbooks, which are well known for limiting consistent winners. It is also an absence of evidence, not a guarantee, so treat it as the starting point for your own check of each venue's current terms.
Why sportsbooks limit winners
A sportsbook sets the odds and takes the other side of your bet. A bettor who wins consistently is a direct cost to it, so limiting that bettor is rational for the book. That is the experience people are comparing prediction markets against.
Why exchanges are structurally different
Kalshi and Polymarket run order books: you trade against other participants, and the venue earns from fees. A profitable trader is not a direct loss to the venue, which removes the main reason a bookmaker would limit you. We say this as a structural point only. It does not bind either platform's future policy.
What we found, and what we did not
- Profit-based limits: none found for Polymarket or Kalshi in public reporting or in the terms we reviewed.
- Winners are concentrated: reporting indicates that most profit on these platforms goes to a small group of accounts, which is consistent with open venues rather than limited ones. Our own breakdown of who loses money covers the other side of that.
- What we could not confirm: private account actions that are not public. If a venue restricted your account for a reason it did not publish, we have no way to see that.
Limits that do exist
- Position caps. PredictIt applies a fixed per-contract cap. See Kalshi vs PredictIt.
- Conduct rules. Both venues added insider-trading rules in 2026. They target conflicts of interest, not profit.
- Regional restrictions. Whether you may trade at all depends on where you live. See the European breakdown.
- API rate limits. These limit request throughput, not winnings.
- Liquidity. In thin markets the real cap on your size is the depth of the book, not a rule.
What this means for arbitrage
Cross-market arbitrage is the least likely strategy to draw attention for winning, since each position is a hedged pair and the edge is thin, a median of roughly 0.7% per position after fees. The practical ceiling is liquidity and capital tied up until resolution, not account limits. The live numbers are on /proof.
Keep the risk in proportion: the real risks are one leg filling without the other and the two listings resolving differently, not being limited. If you want to see how the pair works, see the plans, and read whether it is legal where you live first.
Related articles
- 82% of Polymarket Traders Lose Money
- Is Prediction Market Arbitrage Legal? (2026 Guide)
- Kalshi vs PredictIt: Fees, Limits and Which Is Better in 2026
- How Prediction Market Arbitrage Works
Key terms: CLOB (Central Limit Order Book) · Cross-Market Arbitrage · Spread