Interest calculator — sections 234A, 234B and 234C

Late return, advance tax shortfall and instalment interest, with the full working — for AY 2026-27 returns.

✓Checked against the official Act and rules · verified 28 October 2026

Sections 234A · 234B · 234C

Interest with step-by-step working

Tax on total income

₹

After rebate, including surcharge and cess

TDS + TCS + reliefs

₹

Tax deducted or collected at source, and reliefs

Advance tax paid (amount paid in each window)

Up to 15 June

₹

16 June – 15 September

₹

16 September – 15 December

₹

16 December – 15 March

₹

16 – 31 March

₹

Due date of return

Date of filing (self-assessment tax paid)

Presumptive income — section 44AD / 44ADAResident senior citizen (60+) with no business income

234A–

234B–

234C–

Total interest–

Assessed tax after TDS/TCS: – · Advance tax paid by 31 March: –

Section	Working	Interest

How it works

Section 234A — late return: 1% for every month or part of a month, from the day after the due date to the date of filing, on the tax due after advance tax, TDS, TCS and reliefs.
Section 234B — advance tax shortfall: applies when advance tax paid by 31 March is less than 90% of assessed tax. 1% per month or part of a month from 1 April of the assessment year to the date of filing.
Section 234C — instalments: 3% (1% × 3 months) on the shortfall against 15% by 15 June, 45% by 15 September and 75% by 15 December, and 1% on the shortfall against 100% by 15 March. No interest for June if at least 12% is paid, and none for September if at least 36% is paid.
Presumptive income (44AD / 44ADA): the whole advance tax may be paid by 15 March, so 234C applies only to that instalment.
No advance tax when tax after TDS/TCS is below ₹10,000 (section 208), or for a resident senior citizen with no business or professional income (section 207).
Rule 119A: the amount is rounded down to a multiple of ₹100, and any part of a month counts as a full month.

Please note: this calculator is for the Income-tax Act, 1961 — returns for assessment year 2026-27 (financial year 2025-26) and earlier. It assumes the balance self-assessment tax is paid on the filing date. It does not model the 234C relief for capital gains, dividend or first-year business income — if that applies, the actual 234C will be lower. From tax year 2026-27 the same interest falls under sections 423, 424 and 425 of the Income-tax Act, 2025.

Common questions

How is interest under section 234B calculated?

If advance tax paid by 31 March is less than 90% of assessed tax, simple interest of 1% per month or part of a month is charged on the shortfall, from 1 April of the assessment year to the date the tax is paid. The shortfall is rounded down to a multiple of ₹100.

Is there 234C interest if I paid 12% by 15 June?

No. For the June instalment, interest applies only if less than 12% of the tax was paid by 15 June. For September the safe level is 36%. For December and March there is no such margin — 75% and 100% must be paid.

Do 44AD and 44ADA taxpayers pay 234C interest?

Only on the 15 March instalment. They may pay the whole advance tax by 15 March; if less than 100% is paid by then, interest of 1% is charged on the shortfall.

Which law applies for financial year 2026-27?

The Income-tax Act, 2025 applies from tax year 2026-27. The same interest rules sit in sections 423 (late return), 424 (advance tax shortfall) and 425 (instalments). This calculator covers returns for assessment year 2026-27 and earlier under the 1961 Act.

Sources

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