A legal showdown between a leading prediction market and Illinois over new taxes on sports bets has erupted. Kalshi, one of the largest platforms for such bets, is now suing state officials after being classified as an unlicensed operator.

The stakes are high, with Kalshi facing potential felony charges if it continues to operate without adhering to stricter controls mandated by the state’s new law. This move comes amid a surge in prediction market popularity, driven by major sporting events such as the NBA Finals and World Cup.

For Illinois, the regulation of prediction markets is a pressing issue following a record-breaking loss of $1.5 billion in legal sports betting for residents in 2025. With tech giants like Meta considering entry into this lucrative field, states are eager to establish regulatory frameworks before they become mainstream.

The new law imposes a progressive tax rate on the first and subsequent wagers made through prediction markets, with Kalshi potentially owing as much as 3.5% on every bet placed after the initial $5 million threshold. This could significantly impact its bottom line and operations if enforced.