The German Federal Constitutional Court (BVerfG) held that levying interest on tax deficiencies and tax refunds pursuant to § 233a of the German tax law (AO) is unconstitutional, to the extent that the calculation of interest for “interest periods” (not the assessment period) as from 1 January 2014 was made on the basis of an interest rate of 0.5% monthly because over time, this rate of interest has shown itself to be evidently unrealistic.
Source: KPMG