To claim a rebate in income tax under Section 87A, you should arrive at the gross taxable income by subtracting deductions under 80C to 80U. If your taxable income is below Rs. 5.00 lakhs, you can claim a rebate of Rs.12500 under the old tax regime, and if your taxable is below Rs. 7.00 lakhs, you can claim a rebate of Rs. 25000 under the new tax regime.