63It is accordingly necessary to determine whether the difference in treatment, arising as a result of the legislation at issue, as between persons wishing to transfer their residence to another Member State and those who remain in Spain can be justified by overriding reasons in the public interest, such as those put forward by the Kingdom of Spain and the Member States intervening in support of the forms of order sought by it, namely the effective recovery of tax debts, the balanced allocation between the Member States of powers of taxation and the need to preserve the coherence of the tax system.