The complexity of the individual income tax system can give rise to both under‐ and overreporting of liability, thus creating a wedge between taxpayer perceptions of the price of public services and their actual cost, and potentially leading to budget misallocations and associated efficiency losses. This study uses theory and experiments to evaluate the effectiveness of taxpayer service programs that endeavor to resolve uncertainty over tax liability. To do so, we induce uncertainty over tax liability and investigate the effects of both service accuracy and reliability. We find participants are less likely to file when tax liability is uncertain but the provision of information offsets this effect; furthermore, it appears that simply providing a service, even one that imperfectly reveals liability, increases the propensity to file and the accuracy of the filing. When a service that promises to resolve uncertainty completely is requested but not delivered, the result is underreporting even more severe than in a setting where no service is available. (JEL H2, H26, C91)