The Court declares that, by retaining provisions under which, in respect of the estimation of income relating to unrented immovable property or immovable property rented either to natural persons who do not use them for professional purposes or to legal persons which make such property available to natural persons for private purposes, the tax base is calculated on the basis of the cadastral value so far as immovable property on national territory is concerned, and on the actual rental value so far as immovable property located outside Belgium is concerned, Belgium has failed to fulfil its obligations under Article 63 TFEU and Article 40 of the Agreement on the European Economic Area.