The authors observe that larger errors in forecasting wage tax revenues are accompanied by exceptional changes in the tax code. Beyond these exceptional episodes, the results of this wage tax projection are quite accurate. However, a tendency exists to underestimate the actual amount of revenue. Heterogeneous wage growth explains just a small share of the difference between realization and estimation of the wage tax based on the SOEP. Aggregate updates based on wage tax statistics suggest that changes in household composition or in the composition of the wage tax classes may have caused an underestimation of wage tax revenues based on the update with macroeconomic variables.