Calculate your gross salary by adding Dearness Allowance, House Rent Allowance, Transport Allowance, Special Allowance to your basic pay. Then deduct the exemptions of HRA, professional tax and standard deduction from the gross salary. To the arrived amount, add the extra income of interest, fees, commission and bonus, if any. Add other incomes such as capital gains and income received from renting of properties. Then subtract the basic deductions available under Section 80C, Section 80D and other deductions under Chapter VI A. The income \rarrived is net taxable income. The income tax slab should be decided based on this final income.