# Interest u/s 234A, 234B, 234C Calculator FY 2026-27

> Income tax interest 234B 234C calculator for FY 2026-27, plus 234A: estimate interest for late filing, short advance tax and missed instalments.

Source: https://trykosh.com/tools/income-tax-interest-calculator

Free tool - Income tax

# Income tax interest calculator (234A, 234B, 234C)

Paid advance tax late or not at all? Estimate the interest you owe under 234A, 234B and 234C before you file.

Rules checked 25 October 2026Free - no sign-upRuns in your browser

Interest you owe

INR 6,100

234C: instalments short

INR 4,100

234B: advance tax under 90% (4 months)

INR 2,000

234A: filing after 31 July

INR 0

Total interest

INR 6,100

A simplified estimate: the department rounds periods and amounts in specific ways and adjusts 234B for any self-assessment tax paid before filing.

## Upload your statement and Kosh does this for you.

Upload a bank statement or salary slip and Kosh works out your tax under both regimes from your real numbers, finds the deductions you're missing and reminds you before every deadline.

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## How the 234A, 234B, 234C interest calculator works

Three kinds of interest apply when tax is paid late, each at a simple 1% a month (part of a month counts as a full month). 234C is for missing advance-tax instalments: on the shortfall against 15%, 45%, 75% and 100% of your tax by each due date, for three months each for the first three and one month for the last.

234B applies if, by 31 March, you've paid less than 90% of your tax as advance tax. Interest runs on the unpaid amount from 1 April until you pay it. 234A applies if you file after your due date: 31 July for ITR-1 and ITR-2, 31 August for non-audit ITR-3 and ITR-4 (moved by Budget 2026), and 31 October if your accounts are audited.

Enter your tax after TDS, what you paid in each window, and the month you file. The calculator gives a close estimate; the department's own computation may differ slightly in rounding and in how self-assessment tax paid before filing is treated.

## Worked example: Pooja, a consultant who skipped June

Pooja's tax after TDS is INR 2.4 lakh. She paid nothing by June and INR 60,000 in each later window, INR 1.8 lakh in all, then filed in September. As a consultant filing ITR-4 without an audit, her due date was 31 August. She owes INR 4,920 under 234C, INR 3,600 under 234B (her advance tax fell short of 90%) and INR 600 under 234A for filing one month late: INR 9,120 in total.

Interest you owe

INR 9,120

234C: instalments short

INR 4,920

234B: advance tax under 90% (6 months)

INR 3,600

234A: filing after 31 August

INR 600

Total interest

INR 9,120

A simplified estimate: the department rounds periods and amounts in specific ways and adjusts 234B for any self-assessment tax paid before filing.

[Load this example into the calculator ->](?tax=240000&sep=60000&dec=60000&mar=60000&due=8&fileMonth=9#calculator)

## Good to know

-   Pay any balance as self-assessment tax before you file; interest stops running on what you've paid.
-   234C interest for the June and September instalments isn't charged if you've paid at least 12% and 36% respectively.
-   Late filing also attracts a fee under 234F: INR 5,000, or INR 1,000 if income is up to INR 5 lakh.

## Frequently asked questions

What is the interest rate under 234B and 234C?

Simple interest of 1% a month or part of a month on the shortfall, under all three sections.

Does 234C apply to salaried people?

Only if their tax after TDS is INR 10,000 or more, for example because of capital gains, rent or interest not covered by TDS.

Is interest under 234B charged if TDS covers my tax?

No. Interest is on tax after TDS and TCS. If TDS covers at least 90% of your tax, 234B doesn't apply.

## Sources and assumptions

-   [Income Tax Department](https://www.incometax.gov.in/)

Rules and rates last checked on 25 October 2026. Results are estimates for planning and education, not tax, legal or investment advice. Kosh is an educational financial planning tool by Primedepth Labs. It is not a SEBI-registered investment adviser and does not offer personalised investment advice, hold your money or execute trades. Markets carry risk; read scheme documents carefully and consult a registered adviser before acting.