145. If any person who is resident in Bangladesh in any year proves to the satisfaction of the Deputy Commissioner of Taxes that, in respect of any income which has accrued or arisen to him during that year outside Bangladesh, he has paid tax, by deduction or otherwise, in any country with which there is no reciprocal arrangement for relief or avoidance of double taxation, the Deputy Commissioner of Taxes may, subject to such rules as the Board may make in this behalf, deduct from the tax payable by him under this Ordinance a sum equal to the tax calculated on such doubly taxed income at the average rate of tax of Bangladesh or the average rate of tax of the said country, whichever is the lower. Explanation.-The expression “average rate of tax” means the rate arrived at by dividing the amount of tax calculated on the total income by such income.