Does a simpler income tax yield more equity and efficiency?

This article investigates the impact of tax simplification on various indicators of the efficiency of the tax system and on the distribution of income. The analysis is based on a simulation model (FiFoSiM) using German income tax and household survey microdata. We model tax simplification as the abolition of a set of deductions from the income tax base. We find that this form of tax base simplification leads to a reduction in the use of professional tax advice, a more equitable income distribution and an increase in tax revenue. If this is combined with a reduction of income tax rates to preserve revenue neutrality, the effects depend on the type of rate schedule adjustment. The combination with a flat rate tax increases income inequality at the expense of the middle class, but it also leads to efficiency gains because tax distortions of labour supply are reduced. The combination with a rate schedule adjustment, which preserves the directly progressive schedule reduces inequality but increases overall tax distortions. We conclude that the effects of tax base simplification on after tax income inequality and tax distortions mainly depend on the type of tax schedule adjustment.