48. (1) Notwithstanding that regular assessment in respect of any income is to be made later in any assessment year, and without prejudice to the charge and recovery of tax under this Ordinance after such assessment, the tax on income shall be payable by deduction or collection at source, or by way of advance payment, in accordance with the provisions of this Chapter. (2) Any sum deducted or collected, or paid by way of advance payment, in accordance with the provisions of this Chapter, shall, for the purpose of computing the income of an assessee, be deemed to be the income received, and be treated as payment of tax in due time, by the assessee.