This paper explores the effects of pre-populated personal income tax returns on taxpayers’ tax morale and tax filing behavior. The special questionnaire about Renta Web included in the 2016 wave of the Spanish Institute for Fiscal Studies Fiscal Barometer surveyed individual perceptions about pre-populating income tax returns. Using probit regression analysis, we test whether pre-population affects tax morale. Secondly, we test whether pre-population influences perceptions about tax filing behavior. Our main results show that the relationship between making changes on the prefilled tax form and the likelihood of facing an audit do influence Spaniards’ tax morale, as well as their perceptions about tax filing behavior. Moreover, pre-population features by themselves do not have a clear impact on tax morale or tax filing behavior. Several policy implications arise from the results.