Certificates of residence play an important role in the practice of international tax law. Both the Double Taxation Treaty Relief Regulation (“DBA-Entlastungsverordnung”) and the new section 240a of the Federal Fiscal Code (“Bundesabgabenordnung” – BAO) address the need for these certificates. As a result, in many cases, treaty benefits can only be obtained if the taxpayer who is a resident in the other country can obtain a certificate of residence in that country. Therefore, the direct relief depends on circumstances that the taxpayer cannot influence. Michael Lang examines the resulting treaty and constitutional concerns and discusses possible interpretations compliant with the treaties and the constitution.