Thus the company has the rights to get refund of withholding tax, which is over paid, the interest of withholding tax to shall be calculate since the next day following the due date of three months from the end of the period for filing P.N.D.50 as required by law under Article 1 (1) of the Regulation No. 161 B.E. 2526(1983), Date May 20, 2526(1983).