Advance Tax Interest Calculator (234B & 234C)

If your tax for the year, after TDS, is ₹10,000 or more, you are expected to pay it in instalments during the year rather than in one lump sum when you file. Two different interest charges punish getting this wrong, and they can both apply to the same year.

Section 234C: paying the instalments late

Looks at each due date separately. If the running total you had paid is below the required share on that date, you pay 1% a month on the shortfall: for 3 months on the June, September and December instalments and for 1 month on the March instalment.

Section 234B: paying too little overall

Looks at 31 March. If you had paid less than 90% of the year's tax by then, you pay 1% a month, or part of a month, on the whole shortfall, from 1 April until you pay it.

This calculator follows the Income-tax Act, 1961 as it applies to financial year 2025-26 (assessment year 2026-27) and earlier. The Income-tax Act, 2025 takes over from tax year 2026-27 and renumbers these sections; check the schedule on the income tax portal if you are working out a later year.

The required share is cumulative: each date counts everything you have paid up to that date, not just the latest payment.

• By 15 June: 15% of the year's tax. No section 234C interest if you had paid at least 12%.
• By 15 September: 45%. No section 234C interest if you had paid at least 36%.
• By 15 December: 75%.
• By 15 March: 100%.
• Presumptive taxpayers (section 44AD or 44ADA) pay 100% in one instalment by 15 March, with 1 month of interest on any shortfall.

Tax you pay between 16 and 31 March still counts as advance tax for the 90% test of section 234B, but it does not repair a missed 15 March instalment for section 234C.

234C = shortfall at each date × 1% × 3 months (1 for March) | 234B = (tax − paid by 31 Mar) × 1% × months

• Each shortfall is rounded down to the nearest ₹100 before interest is worked out.
• Section 234B applies only if less than 90% was paid by 31 March, and then it is charged on the full shortfall, not just on the part above the 90% line.
• Section 234C is charged on each instalment separately, so a founder who pays everything on 15 March still owes interest on the three earlier instalments, unless the 12% and 36% relief applies.

• Anyone whose tax for the year, after TDS and TCS, is under ₹10,000. Neither section applies.
• A resident senior citizen with no income from business or profession, who can simply pay the tax when filing.
• Salaried people whose tax is fully covered by TDS from their employer.

A shortfall caused by income you could not have predicted, such as capital gains, lottery winnings, dividends or first-time business income, is not penalised under section 234C if you pay the extra tax in the remaining instalments. This calculator does not model that relief, so if it applies to you, treat the result as an upper figure.

• Estimate your year's income in June and pay 15% of the tax. Paying at least 12% already removes the June interest.
• Top up on 31 March if you are short. It will not fix section 234C for the March instalment, but it can lift you past the 90% test and wipe out section 234B altogether.
• Pay the balance as soon as you know the number. Section 234B runs by the month until you pay.
• Check your advance tax challans against your tax statement before filing. An unreported payment is the most common reason the interest looks too high.

• Entering the amount of each payment instead of the running total. The schedule is cumulative.
• Confusing section 234A with 234B and 234C. Section 234A is interest for filing the return late; use our ITR late fee calculator for that.
• Assuming 234B only covers the part below 90%. When it applies, it covers the whole shortfall.
• Counting days instead of months. A part of a month is charged as a full month.

From tax year 2026-27 (income earned from 1 April 2026) the Income-tax Act 2025 replaces the 1961 Act. This page uses the 1961 section numbers, which still apply to FY 2025-26 and earlier years. For the current year, the same rules sit under these new numbers:

• Section 234A → section 423 of the Income-tax Act 2025
• Section 234B → section 424 of the Income-tax Act 2025
• Section 234C → section 425 of the Income-tax Act 2025