Tax deduction timing clarified: payment deadlines revised; deduction allowed where tax is later withheld and subsequently paid. Amendment to section 40(a)(ia) fixes payment-based timing for disallowance: tax deducted in the last month requires payment by the return due date, otherwise payment must be by the last day of the previous year; a proviso allows deduction if tax is deducted later or paid after those dates provided it is ultimately paid in the year in which payment occurs. Sub-clause (ib) is omitted, consolidating the temporal tests and permitting relief where tax is subsequently paid.