A full overview of the German tax system can be found in the brochure of the Ministry of Finance An ABC of Taxes. . Organization for Economic Cooperation and Development Circular 23.02.1983 – Administrative Principles 1983 (Management Principles) (No. 138 AO Advertisements on Professional Activity [pdf, 40KB]) Please note that this is not an exhaustive list. These work translations are provided as a courtesy by the language department of the federal Department of Finance and are only used for informational purposes. Only German-language versions are decisive for law enforcement. Please note that the translations have not been coordinated with other public administrations in Germany. I R 73/16 – Adjustment of income under Section 1 (1) of the External Tax Relations Act with respect to the amortization of an unsecured loan within a group of companies [pdf, 180KB] (I R 51/17 – Income Correction After .