Interest for default in advance tax: 1% per month from 1 April where advance tax is unpaid or insufficient. Interest is payable where advance tax is unpaid or less than 90% of the assessed tax at simple interest of 1% per month from 1 April of the assessment year. The amount on which interest is computed is the tax determined on assessment, less reliefs and credits (sections 89/90/90A/91, MAT/AMT credits, TDS/TCS) and advance tax. Interest paid under section 140A reduces liability under section 234B, and adjustments follow consequential changes from assessment, rectification or settlement commission orders.