Kalshi posts record Masters volume as Polymarket tightens rules

Kalshi said it recorded about $500 million in trading volume over the Masters weekend, covering player props, winner markets and side bets. The exchange posted an image on its social account showing the total.

The company said the activity included a mix of retail traders and institutional participants across multiple event markets. The figure follows other large event volumes the exchange has reported in past major sports and political markets.

Polymarket updated its market integrity rules to ban trading on confidential information that violates a duty of trust and to prohibit market manipulation on both its decentralized finance products and its central exchange. The revised terms bar tipping friends or allowing officials with the power to influence outcomes to place bets. Penalties listed include wallet bans, referrals to law enforcement, fines, suspensions and account terminations.

Neal Kumar, Polymarket’s chief legal officer, described the revisions: “Markets thrive on clarity. These enhancements make expectations abundantly clear for every participant.”

The policy changes follow scrutiny of suspiciously timed wagers on prediction market platforms. Earlier this year a roughly $32,000 position on Polymarket betting on the removal of Venezuela’s Nicolás Maduro was placed hours before reported U.S. troop movements and later paid out more than $400,000. That trade drew attention from lawmakers.

Representative Ritchie Torres introduced the Public Integrity in Financial Prediction Markets Act of 2026, which has more than 40 Democratic co-sponsors and would make trading on material non-public government information unlawful.

Polymarket said it will also take action against third-party startups and builders accused of directing liquidity or data to support copytrading strategies tied to suspected insider information. The company said enforcement will target individual traders and services that amplify non-public information through automated strategies.

Kalshi has taken enforcement actions on its platform in prior cases. The exchange suspended a video editor associated with a prominent content creator for trading on non-public information, fined and banned a California gubernatorial candidate for betting on their own race, and declined to pay out on a market tied to the death of Iran’s supreme leader, returning fees and settling at the last traded price.

Trading volumes around major events have increased on both regulated and decentralized prediction platforms. Several operators have announced expanded compliance and enforcement measures intended to deter trading based on confidential government or corporate information and to limit services that replicate suspect trading strategies.