42In that connection, first, it has been consistently held that the right of taxable persons to deduct the VAT due or already paid on goods purchased and services received as inputs from the VAT which they are liable to pay is a fundamental principle of the common system of VAT established by the relevant European Union legislation (see, inter alia, Commission v Italy, paragraph 28; Sosnowska, paragraph 14; and Enel Maritsa Iztok 3, paragraph 31).