Rising self-employment rates in U.S. tax data that are absent in survey data have led to speculation that tax records capture a rise in new “gig” work that surveys miss. Drawing on the universe of IRS tax returns, we show that trends in firm-reported payments to “gig” and other contract workers do not explain the rise in self-employment reported to the IRS; rather, that increase is driven by self-reported earnings of individuals in the EITC phase-in range. We isolate pure reporting responses from real labor supply responses by examining births of workers’ first children around an end-of-year cutoff for credit eligibility that creates exogenous variation in tax rates at the end of the tax year after labor supply decisions are already sunk. We find that exposing workers with sunk labor supply to negative marginal tax rates results in large increases in their propensity to self-report self-employment – only a small minority of which leads to bunching at kink-points. Consistent with pure strategic reporting behavior, we find no impact on reporting among taxpayers with no incentive to report additional income and no effects on firm-reported payments of any kind. Moreover, we find these reporting responses have grown over time as knowledge of tax incentives has become widespread. Quantitatively, our results suggest that as much as 59 percent of the growth in self-employment rates, and all counter-cyclicality, can be attributed to changes in reporting behavior that are independent of changes in the nature of work. Our findings suggest caution is warranted before deferring to administrative data over survey data when measuring labor market trends.