This paper attempts to identify present-biased procrastination in tax filing behavior. Our exercise uses dynamic discrete choice techniques to develop a counterfactual benchmark for filing behavior under the assumption of exponential discounting. Deviations between this counterfactual benchmark and actual behavior provide potential "missing-mass" evidence of present bias. In a sample of around 22,000 low-income tax filers we demonstrate substantial deviations between exponentially-predicted and realized behavior, particularly as the tax deadline approaches. Present-biased preferences not only provide qualitatively better in-sample fit than exponential discounting, but also have improved out-of-sample predictive power for responsiveness of filing times to the 2008 Economic Stimulus Act recovery payments. Additional experimental data from around 1100 individuals demonstrates a link between experimentally measured present bias and deviations from exponential discounting in tax filing behavior.