The explosion of sports betting has meant billions of dollars in revenue for gaming operators, but the IRS is leaving big money on the table, a government watchdog found.

A Treasury Inspector General for Tax Administration review of roughly 43 million forms during tax years 2018 through 2020, totaling about $156 billion issued to taxpayers, found about 150,000 individuals who won over $15,000 but didn’t file a tax return on those earnings, a new Thursday report said. In response to the review, the IRS determined it could potentially increase tax revenue by about $1.4 billion by addressing some of those …