Instantly calculate interest for late ITR filing (234A), advance tax shortfall (234B), and missed instalments (234C) — free, accurate, AY 2026-27 ready.
Frequently asked questions
| Installment | Due Date | Required % | Interest Period |
|---|---|---|---|
| 1st | 15 June | ≥ 15% | 3 months |
| 2nd | 15 September | ≥ 45% | 3 months |
| 3rd | 15 December | ≥ 75% | 3 months |
| 4th | 15 March | 100% | 1 month |
For the formulas, worked examples and detailed explanation, read the Section 234A, 234B, 234C Interest (2026) guide.
This Section 234A 234B 234C Interest Calculator is a free tool that computes simple interest charged under Sections 234A, 234B, and 234C of the Income Tax Act, 1961 — the three provisions that penalise late filing and unpaid advance tax. It's built for salaried employees, freelancers and content creators, small business owners, traders, NRIs, and CAs who need a quick, reliable number before they file or advise a client. Instead of manually tracking due dates and instalment percentages, you get all three interest figures in one place.
All three sections use the same core rate — 1% simple interest per month or part of a month — but the base amount and time period differ. This is laid out under Rule 119A of the Income-tax Rules, 1962, which governs how the period and amount are rounded.
Section 234A (late filing):
Interest = 1% × (Tax liability − TDS/TCS − Advance tax paid) × Months late
(Months counted from day after due date to date of filing; part month = full month)
Section 234B (advance tax default, triggers only if advance tax paid < 90% of assessed tax):
Interest = 1% × (Assessed tax − Advance tax paid) × Months
(Months counted from 1 April of the assessment year to date of payment/assessment)
Section 234C (deferment of instalments):
Interest = 1% × Shortfall in each instalment × 3 months (1 month for the last instalment)
(Instalment shortfall = required % of tax minus tax paid — with 12%/15 Jun and 36%/15 Sep tolerance)
For the amount on which interest is calculated, fractions are rounded down to the nearest ₹100 as per Rule 119A. Sections 234B and 234C only apply if your net tax payable (after TDS) is ₹10,000 or more — this is the advance tax threshold under Section 208 of the Income Tax Act, 1961. Below that, advance tax isn't mandatory, so no interest is charged under either section.
Meet Rohan, a freelance content creator. His total tax liability for FY 2025-26 is ₹1,20,000. TDS deducted during the year is ₹20,000. He paid ₹40,000 as advance tax (in one lump sum on 15 March, so nothing by the June, September, or December instalment dates). His ITR due date is 31 July 2026, but he files on 15 October 2026 — 3 months late.
Section 234A: Base = ₹1,20,000 − ₹20,000 − ₹40,000 = ₹60,000 Months late = 3 (August, September, October) Interest = 1% × ₹60,000 × 3 = ₹1,800
Section 234B: Assessed tax = ₹1,20,000 − ₹20,000 = ₹1,00,000 Advance tax paid (₹40,000) is 40% of assessed tax — below the 90% threshold, so 234B applies. Base = ₹1,00,000 − ₹40,000 = ₹60,000 Months from 1 April 2026 to 15 October 2026 = 7 Interest = 1% × ₹60,000 × 7 = ₹4,200
Section 234C: Net tax = ₹1,00,000. Required cumulative: 15% by 15 Jun (₹15,000), 45% by 15 Sep (₹45,000), 75% by 15 Dec (₹75,000), 100% by 15 Mar (₹1,00,000). Rohan paid ₹0 by 15 Jun, 15 Sep, and 15 Dec, so shortfalls of ₹15,000, ₹45,000, and ₹75,000 each attract interest for 3 months. By 15 March he had paid only ₹40,000 in total — still ₹60,000 short of the full ₹1,00,000 — so the last instalment also attracts interest, for 1 month. Interest = 1% × 3 × (₹15,000 + ₹45,000 + ₹75,000) + 1% × 1 × ₹60,000 = ₹4,050 + ₹600 = ₹4,650
Total interest payable: ₹1,800 + ₹4,200 + ₹4,650 = ₹10,650
Enter these same figures into the calculator above and it returns this exact breakdown.
See the Section 234A, 234B, 234C Interest (2026) guide for the full 234C exception and worked examples.
The ITR due date for FY 2025-26 (AY 2026-27) — the year this calculator is built around — is 31 July 2026 for individuals not subject to audit. If you're reading this after that date and haven't filed, Section 234A interest is already running.
The Income-tax Act, 2025 replaces the Income-tax Act, 1961 from 1 April 2026, and it renumbers these very sections — 234A becomes Section 423, 234B becomes Section 424, and 234C becomes Section 425, under the new Income-tax Act, 2025. The 1% per month rate and computation logic stay the same. Returns for FY 2025-26 (AY 2026-27) — filed now — still fall under the old 234A/234B/234C numbering; the new numbering applies to Tax Year 2026-27 onward.
234A charges interest for filing your ITR after the due date. 234B charges interest if you paid less than 90% of your assessed tax as advance tax. 234C charges interest for missing the quarterly advance tax instalment percentages, even if you pay the full amount by year-end.
If that additional income is irregular freelance or content income, you can also check it with the Advance Tax & 234B/234C Interest Calculator for Freelancers.
No. Section 234B only applies if your net tax payable (after TDS) is ₹10,000 or more and you paid less than 90% of assessed tax as advance tax. Below ₹10,000, advance tax isn't mandatory.
Yes, resident senior citizens (60+) without business or professional income are exempt from paying advance tax, and therefore from interest under Sections 234B and 234C.
No. Section 234A interest is charged for the delay in filing the return itself, separate from the tax payment. You need to both pay the balance tax and file the return to stop the interest clock.
Under Rule 119A, any part of a month is treated as a full month. Filing even one day into a new month adds a full month's interest.
No. The rate and logic remain 1% per month simple interest — only the section numbers change (234A/B/C become 423/424/425) from Tax Year 2026-27 onward.
Calculations verified by our team including CA Anita Patil. View our full accuracy policy and meet the team →
For informational purposes only. Results are estimates based on the inputs you provide and the rules in effect for the period shown, and are not tax, legal or financial advice. Verify figures against the relevant official source and consult a qualified professional before acting on them. Accuracy & limitations
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