ABSTRACT This study examines whether taxpayers intentionally avoid Internal Revenue Service (IRS) third‐party reports. In 2017 an IRS amendment created a quasi‐exogenous shock that reduced third‐party tax reporting of pari‐mutuel gambling winnings from certain types of wagers. I consider the effect that this rule change had on taxpayer behavior. Using a difference‐in‐differences research design comparing thoroughbred racing in the United States to Canada, I find a 27% increase in gambler's investment into wager‐types that became less likely to trigger third‐party reports. Further, I provide evidence that this effect was because of third‐party reporting, not withholding, and was stronger in more informed gambling populations. These findings suggest that taxpayers knowingly avoid third‐party reports, enabling underreporting of income to the IRS. This has important policy implications because underreported individual income is the largest driver of the $496 billion annual gap between legal tax liability and actual tax collections in the United States.