Three different sections, three different triggers, all charging the same 1% per month interest - but for entirely different reasons. Understanding which one applies to you (sometimes all three at once) can save you from a surprisingly large interest bill at filing time.
Sections 234A, 234B, and 234C each levy simple interest at 1% per month or part of a month on the relevant shortfall amount. "Part of a month" means even a single day's delay counts as a full month for interest computation - there's no proportionate calculation.
If you file your ITR after the due date, and there is tax payable (i.e., self-assessment tax that wasn't already paid via TDS/advance tax), interest under Section 234A is charged at 1% per month from the day after the due date until the date of actual filing, on the unpaid tax amount.
Section 234B applies if you were liable to pay advance tax (i.e., your total tax liability for the year, after TDS, exceeds ₹10,000) but either:
Interest is charged at 1% per month from 1 April of the assessment year until the date of payment of self-assessment tax (or completion of assessment), on the shortfall between 90% of the assessed tax and the advance tax actually paid.
Even if you pay 90%+ of your tax by year-end (avoiding 234B), you can still owe interest under 234C if you didn't pay advance tax on time, in each instalment. The advance tax schedule for individuals/non-corporate assesses is:
| Due Date | Cumulative Advance Tax Required |
|---|---|
| 15 June | 15% of estimated tax |
| 15 September | 45% of estimated tax |
| 15 December | 75% of estimated tax |
| 15 March | 100% of estimated tax |
If the cumulative advance tax paid by each due date is less than the required percentage, interest at 1% per month is charged on the shortfall for that instalment - typically for 3 months for the first three instalments and 1 month for the last, though the exact period and formula vary slightly by case.
Yes. It's entirely possible for a taxpayer to owe interest under 234A (late filing), 234B (insufficient total advance tax), and 234C (instalments not paid on schedule) all in the same year - for example, someone with significant capital gains late in the year who didn't revise their advance tax estimate and then also filed their return late.
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