S.37(1): Business expenditure-Amortisation of expenditure-expenditure on voluntary retirement scheme Employees at time of retirement paid gratuity and leave encashment-Allowable as business expenditure-Sums payable-Payments brought within scope of disallowance with effect from 1-4-2002-Provision not applicable to payments prior to that date. Allowable without any condition of actual payment prior to such date. [S. 35DD, 43B(f), 260A]