The European Court of Justice (ECJ) issued a decision on 28 February 2013 in the case of Dr. Manfred Beker and Christa Beker v Finanzamt Heilbronn. A preliminary ruling from the ECJ had been requested by the Federal Finance Court. The case concerned the application of Article 63 of the Treaty on the Functioning of the European Union (TFEU) to the German rules on foreign tax credits.

The ECJ was asked to rule on whether in the context of double tax treaties Germany could apply a system for eliminating double taxation on foreign income of individuals that offset foreign tax. And the ECJ held that a system of multiplying the amount of tax due on total (domestic and foreign) income by the proportion that the foreign income bears to the total income, without taking into account the special costs relating to personal and family circumstance, was precluded by Article 63 TFEU.