In principle, the tax overstated by 3% or 2% is owed in accordance with § 14c (1) UStG. An input tax deduction is only possible in the legally applicable amount (16% or 5%). This also applies if the entrepreneur was unable to convert his cash register system in time for 01.07.2020.
There is a simplification rule for supplies to other traders in July 2020 (margin note 46).
Die genannten Rz. beziehen sich auf das BMF-Schreiben vom 30.06.2020 a.a.O.