“relevant dividend”) which becomes payable to any non-resident person if the relevant dividend consists, of the whole or any part of the amount of a dividend not being the whole or any part of a dividend which is exempt from income tax under this Act, distributed by any quoted public company and receievd, either directly or through one or more intermediary companies, by such resident company, income tax equivalent to fifteen per centum of such relevant dividend and the amount of the income tax which a residentt company is under this section, required to deduct shall be a debt due from such resident company to the State and shall be recoverable forthwith as such or may be assessed and charged upon such resident company in addition to any income tax otherwise payable by it :