What the law says this year
The Income-tax Act, 2025 took effect on 1 April 2026. The new-regime slabs are in section 202. The rebate, including marginal relief just above ₹12 lakh of taxable income, is in section 156. Before 1 April 2026 those rules were section 115BAC and section 87A. The Finance Bill 2026 memorandum says the rates are unchanged for tax year 2026-27.
A salaried person with ₹13 lakh of salary pays ₹26,000 in the new regime after marginal relief and cess. At ₹12.8 lakh the tax is ₹5,200. Both figures include 4% cess. Cess itself has no marginal relief.