For a long time, the interest rate of 6% p.a. seemed to be set in stone in tax law. For a very long time, the interest rate was particularly painful in the case of additional tax claims, for example due to a tax audit or following a subsequent declaration or criminal tax proceedings. With a seemingly secure source of additional tax payments, the tax authorities were able to generate enormous revenues with the core standards of Sections 233a in conjunction with 238 AO, even in times of persistently low interest rates on the money market. Initial criticism of the high interest rates of a constant 6% went virtually unheard in the legislative process.

However, in its ruling of 3 September 2018 (VIII B 15/18), the BFH proclaimed for the second time that it had constitutional concerns about the level of the interest rate (see previously BFH of 25 April 2018, IX B 21/18).

What are the consequences of these shake-up judgements by Germany's highest fiscal court?

Affected taxpayers should definitely lodge a corresponding appeal. According to the letter dated 14 June 2018, the BMF grants suspension of enforcement. Due to the above BFH ruling, this has now been extended to periods from April 2012 (BMF dated 14 December 2018).

Ultimately, the BVerfG will have to decide again after it rejected a similar constitutional complaint for earlier years (BVerfG of 3 September 2009, 1 BvR 2539/07). The continued attack on the high tax interest rate may also soon have an impact on legislation that could lead to a tax "interest rate reduction" (cf. e.g. FDP amendment, BT-Drucks. 19/5613).