As of Oct. 1, the Internal Revenue Service is charging 8% interest on estimated tax underpayments, up from 3% two years ago. The increase is one of the many effects of rising interest rates.

Here’s a good bet: Millions of fans of online sports gambling have no idea they’re racking up big tax bills on their wagers—at least as the Internal Revenue Service sees it. Sports betting has exploded since 2018, when the Supreme Court struck down a national ban, and it’s now legal in 37 states and the District of Columbia.