Section 234A/B/C Interest Calculator
Estimate the interest for late ITR filing, default in advance tax and deferment of instalments — 1% per month, live and section-wise.
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- Rules cited on the page
Enter your figures — the result on the right updates as you type.
Section-wise breakdown
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We compute the exact interest, plan your advance tax and file your return on time.
Disclaimer: Indicative estimate only. Actual interest under Sections 234A/234B/234C depends on the exact dates and amounts of each payment and the final assessed tax. Interest is charged at 1% per month or part of a month.
Interest for defaults — Section 234A/B/C
When you miss the ITR due date, underpay advance tax, or defer your advance-tax instalments, the Income Tax Act charges simple interest at 1% per month or part of a month. This calculator splits that interest into the three relevant sections so you can see exactly where it comes from.
What each section covers
All three run on assessed tax = total tax liability minus TDS/TCS. 234A depends on how late you file; 234B and 234C depend on how much advance tax you paid, and when.
| Trigger | ITR filed after due date |
| Base amount | Assessed − advance tax |
| Rate | 1% / month |
| Period | Due date → filing |
| Trigger | Adv. tax < 90% assessed |
| Base amount | Assessed − advance tax |
| Rate | 1% / month |
| Period | 1 Apr of AY → payment |
| Trigger | Instalment shortfall |
| Base amount | Shortfall at each date |
| Rate | 1% / month |
| Period | 3 · 3 · 3 · 1 months |
Worked example
Total tax liability ₹1,50,000, TDS ₹30,000, no advance tax paid, ITR filed 3 months late (234A) and shortfall outstanding for 4 months (234B). Assessed tax = ₹1,50,000 − ₹30,000 = ₹1,20,000.
Interest computed section-wise
Key terms explained
Assessed tax
Your total tax liability minus TDS/TCS credit. It is the figure advance tax is measured against — advance tax should cover at least 90% of it to escape Section 234B.
Part of a month
Interest is charged for every month or part of a month. Even a single day into a new month is rounded up to a full month, so filing on the 1st vs the 28th makes no difference to the count.
90% rule (234B)
If the advance tax you paid is less than 90% of assessed tax, 234B interest applies on the whole shortfall from 1 April of the assessment year until you pay.
Instalment schedule (234C)
Advance tax is due in four instalments — cumulatively 15%, 45%, 75% and 100% by 15 Jun, 15 Sep, 15 Dec and 15 Mar. Missing a milestone triggers 234C on that shortfall.
Questions people ask
Short answers on Interest 234A/B/C Calculator. Tap a question to open it.
01What is interest under section 234A?
Interest at 1% per month or part of a month on the unpaid tax, for the period from the due date of filing the return until it is actually filed. It applies only where tax remains payable after TDS and advance tax.
02When does section 234B apply?
Where advance tax paid during the year is less than 90% of the assessed tax. Interest runs at 1% per month from 1 April of the assessment year to the date of determination, on the shortfall.
03How is 234C different?
Section 234C charges 1% per month for a shortfall in each individual instalment — 15% by 15 June, 45% by 15 September, 75% by 15 December and 100% by 15 March — for three months each for the first three and one month for the last.
04Can I get relief from 234C for unexpected income?
Yes. Shortfalls attributable to capital gains, winnings from lotteries, dividend income or first-time business income are excluded, provided the tax on that income is paid in the remaining instalments or by 31 March.
05Is the interest calculated on part months?
Yes. Any part of a month counts as a full month for all three sections, which is why filing even a day into a new month adds a full month of interest.
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Disclaimer: This tool gives indicative results for general guidance only and is not professional advice. Please verify with a qualified CA before acting on the numbers.