18It follows that the principle of equal treatment, in matters relating to tax, does not coincide with the principle of fiscal neutrality. Accordingly, by submitting in its application, in particular, that the ML, by restricting the possibility of forming a VAT group to undertakings in the financial and insurance sectors, is incompatible with the principle of equal treatment, when it relied in that regard on the principle of fiscal neutrality in the reasoned opinion, the Commission has extended the subject-matter of the dispute.