The statute enjoins the employer to compute the tax liability of the employee on the basis of the rates in force and to deduct the tax at the average rate computed on the basis of the same. Thus, the employer is required to compute at the beginning of the financial year, the total salary income payable to an employee during the financial year. Further, the employer should also take into account any other income as reported by the employee. After considering the incomes exempt, deductions and relief, the tax liability of the employee should be determined on the basis of the rates in force for the financial year. Every month, 1/12 of this net tax liability as computed above is required to be deducted.