Prof. Dr. Tappen and Prof. Dr. Varnholt have for many years been active in advising on tax planning for real estate transactions and their management (Property Management). A special focus of their expertise is on the tax optimisation of cross-border transactions with regard to questions of financing.

Renewable energy sources
AThe investment in renewable energy sources presents the advisor a multi-disciplinary task. The TCS Treuhand Steuerberatungsgesellschaft GmbH combines an almost unique range of expertise in this field.
Prof. Dr. Tappen, together with his partners and colleagues, regularly publishes on this subject (refer to the latest publication "Renewable sources of energy, cross-border strategies and country reports" appearing in the Frankfurt School Verlag).

Furthermore, Prof. Dr. Tappen is joint publisher of a renowned interdisciplinary blog about renewable energy sources.