(8) If, for any reason, the contribution or any portion thereof leviable under this section has escaped assessment in any year, whether before or after the commencement of this Act, the Chief Executive Officer may, within five years, from the last date of the year to which such escaped assessment relates serve upon the mutawalli a notice assessing him with the contribution or portion thereof which had escaped assessment, and demanding payment thereof within thirty days from the date of service of such notice, and the provisions of this Act and the rules made thereunder, shall, as far as may be, apply as if the assessments were made under this Act, in the first instance.