On 1 February 2006, the Belgian Constitutional Court (Arbitragehof/Court d'Arbitrage) decided on the different taxation of interest on debt claims derived by a Luxembourg permanent establishment (PE) of a Belgian enterprise, and by a Belgian professional who has a fixed base in Luxembourg, under the Belgium-Luxembourg income and capital tax treaty of 17 September 1970 (the treaty). A preliminary ruling was requested by the Court of First Instance Aarlen on 9 February 2005. (a) Facts. The taxpayer was a dentist resident in Belgium, who exercised his profession in Luxembourg, where he had a fixed base. Furthermore, he had a savings...