Prediction markets, the online platforms where users take positions on the outcome of real-world events, have been quietly amassing scale for the past two years. Polymarket, the largest, facilitated around $138,000 (£103,000) in trading during the entire 2022 World Cup. By June 2026, trading volume across three major prediction market platforms reached $44bn, the recent World Cup being the latest catalyst.

For accountants and their clients, that matters: prediction market activity is coming to an inbox near you, and the tax questions it raises are not straightforward.