ARTICLE 27
Procedural Rules for Taxation at Source
(1) In cases in which payments may be taxed at limited rates or not taxable in the State of source each Contracting State provides for procedures that the payer can make the payments as provided for in this Convention.
(2) The competent authorities may by mutual agreement implement the provisions of this Article and if necessary establish other procedures for the implementation of tax reductions or exemptions provided for under this Convention. The Contracting State in which the items of income arise may ask for a certificate by the competent authority on the residence in the other Contracting State.
(3) Any refund applications must be submitted by the end of the fourth year following the calendar year in which the withholding tax was applied to the dividends, interest, royalties or other items of income.