“whether a transaction which comprises several elements is to be regarded as a single supply or as two or more distinct supplies to be assessed separately.”
“In this respect, taking into account, first, that it follows from art 2(1) of the Sixth Directive that every supply of a service must normally be regarded as distinct and independent and second, that a supply which comprises a single service from an economic point of view should not be artificially split, so as not to distort the functioning of the VAT system, the essential features of the transaction must be ascertained in order to determine whether the taxable person is supplying the customer, being a typical customer, with several distinct principal services or with a single service. There is a single supply in particular in cases where one or more elements are to be regarded as constituting the principal service, whilst one or more elements are to be regarded, by contrast, as ancillary services which share the tax treatment of the principal service. A service must be regarded as ancillary to a principal service if it does not constitute for customers an aim in itself, but a means of better enjoying the principal service supplied.”
“where two or more elements or acts supplied by a taxable person to a customer, being a typical consumer, are so closely linked that they form objectively, from an economic point of view, a whole transaction, which it would be artificial to split, all those elements or acts constitute a single supply for purposes of the application of VAT.”
“it is apparent that the customisation in question is neither minor nor ancillary but, on the contrary, predominates; such is the case in particular where in the light of factors such as its extent, cost or duration the customisation is of decisive importance in enabling the purchaser to use the customised software.”