This paper analyzes a 1992 decrease in U.S. federal income tax withholding that shifted the timing of income tax payments while leaving ultimate tax burdens unchanged. Consequently income typically received as a lump-sum refund on filing a tax return was shifted into the previous year's monthly income. This paper considers the impact of the withholding change in the context of mental accounting and finds a decrease in the probability that households contributed to a tax-preferred retirement account. Additional robustness tests show that short-term saving did not simultaneously increase and that the main findings are not driven by liquidity constraints.

We develop an empirical test for whether households understand or misperceive their marginal tax rate. Our identifying variation comes from the loss of the Child Tax Credit when a child turns 17. Using this age discontinuity, we find that despite this tax liability increase being lump-sum and predictable, households reduce their reported wage income upon discovering they have lost the credit. This finding suggests that households misinterpret at least part of this tax liability change as an increase in their marginal tax rate. This evidence supports the hypothesis that tax complexity can cause confusion and leads to unintended behavioral responses. (JEL D12, D14, H24, H31)