All tax policies must be agreed unanimously, so Ireland retains an effective veto
This article specifically relates to harmonising legislation on turnover tax, excise duties and other forms of indirect taxation (approval subject to unanimity of the Council of Ministers).
As Peter Sutherland has pointed out, it relates, therefore, to taxation on goods. Corporation tax is a form of direct taxation and is not affected by this article. At any rate, the ECJ (Case C-338/01) has already ruled that the term “fiscal provisions” covers all areas and aspects of taxation, which must be provided for on a unanimous basis.