The four instalments
For individuals, advance tax is due as cumulative percentages of your estimated annual tax: 15% by 15 June, 45% by 15 September, 75% by 15 December, and 100% by 15 March. Each date is a cumulative target, so you pay up to the percentage due by then.
Interest for missing it
Pay an instalment short and Section 234C charges interest on the shortfall for that quarter. If your total advance tax for the year falls short, Section 234B charges interest from 1 April until you pay. The interest is 1% per month, so delays add up. Presumptive-income taxpayers have a single 15 March date — confirm your category.
A worked example
Example: your estimated tax (after TDS) is ₹1 lakh. You should pay ₹15,000 by 15 June, ₹45,000 (cumulative) by 15 September, ₹75,000 by 15 December and the full ₹1 lakh by 15 March. Pay nothing until March and you owe 234B/234C interest on the earlier shortfalls. Estimating early and paying on schedule avoids it. See whether you need to pay at all. Our team can schedule your instalments.