ITR Late Filing Fee & Interest Calculator

The fee is flat. The interest is not.

The late-filing fee is a fixed statutory amount and it is the part everyone fixates on. It is ₹5,000, reduced to ₹1,000 where total income does not exceed ₹5,00,000, and it does not change whether you are one day late or eleven months late. Because it is flat, it creates no urgency: once you have missed the due date, the fee is already incurred and there is nothing further to lose by waiting. That is precisely the wrong intuition, because the fee is not where the money is.

The money is in interest, and interest is a function of time. Two separate provisions run at once. Late-filing interest, the charge formerly under Section 234A, runs at 1% per month or part month on unpaid tax from the due date until you file. Section 424 of the Income-tax Act, 2025 — old Section 234B — runs at a further 1% per month or part month from 1 April of the assessment year until payment, and applies whenever advance tax and TDS together fell short of 90% of the assessed tax. Both are simple interest, both count any part of a month as a whole month, and both stack. For a taxpayer with a genuine shortfall, the combined rate is 2% a month, or 24% a year, on the unpaid balance.

A worked case makes the proportions clear. A business filer for FY 2025-26 with ₹6,00,000 of tax and only ₹1,00,000 paid, filing on 10 November 2026 instead of 31 July 2026, owes a ₹5,000 fee, ₹20,000 of late-filing interest (four part months on ₹5,00,000) and ₹40,000 under Section 424 (eight part months from 1 April). Total ₹65,000 — of which the fee, the number everyone worries about, is under 8%. Waiting one further month adds ₹10,000, or twice the entire fee. That is the shape of the problem: the headline penalty is small and static, the real cost is invisible and compounding.

The largest number on the page is usually the losses you lose

If you had a loss for the year, everything above is a footnote. The law permits business losses and capital losses to be carried forward and set off against future income, which is what makes an early-stage business or a bad year in the market survivable — a ₹20 lakh loss carried forward is ₹20 lakh of future profit that will not be taxed. That right is conditional on filing the return by the due date. Miss it, and the loss is not reduced or deferred; it is gone. There is no application, no condonation as of right, and no amount of interest paid later that restores it.

Value it and the asymmetry is stark. On a ₹8,00,000 business loss taxed at 30%, the forfeiture costs about ₹2,40,000 of future tax against a ₹5,000 fee — a factor of forty-eight. On a larger loss the ratio is the same and the rupees are worse. This is the single most expensive consequence of late filing in the Indian tax system, and it is the one least understood, because nothing about it appears on the challan. You simply pay more tax in some later year and never connect it to a return filed in September rather than July.

Two refinements are worth knowing. House property loss is the exception — it can be carried forward even where the return is filed late, so a taxpayer whose only loss is unabsorbed interest on a let-out property is not affected. And unabsorbed depreciation is treated differently from a business loss and survives a late return. Everything else — business loss, speculation loss, short-term and long-term capital loss — depends on filing by the due date. If you have any of those and the due date is approaching, filing an incomplete return on time and revising it later is almost always the right call, because a revised return preserves the original filing date for this purpose while a belated one does not.

Which deadline actually applies to you

There are three dates for any assessment year and most people know only the first. The original due date is 31 July of the assessment year for ordinary taxpayers and 31 October for those subject to tax audit under Section 63 of the Income-tax Act, 2025. Filing by this date costs nothing, preserves loss carry-forward, and avoids late-filing interest entirely. The belated return deadline is 31 December of the assessment year. Between the two, you can still file a complete and valid return: you pay the fee and the interest, and you lose the carry-forward right, but the return itself is a normal one and a refund can still be claimed. The same date is the deadline for revising a return already filed.

After 31 December the ordinary window closes and only an updated return remains. This can be filed within 48 months from the end of the relevant assessment year, and it carries additional tax on top of the tax and interest otherwise payable — 25% if filed within twelve months of the end of the assessment year, 50% within twenty-four months, 60% within thirty-six months and 70% within forty-eight months. For FY 2025-26 that means an updated return is available until 31 March 2031, at rising cost.

The updated return has two restrictions that matter enormously and catch people out constantly. It cannot be used to claim a refund, to increase a refund, or to reduce the tax payable, and it cannot be used to report a loss. Its purpose is to let a taxpayer voluntarily declare additional income and pay more tax, not to fix an omission in their own favour. So if the department owes you money — TDS deducted on interest or contract payments against a liability you never had — and you let 31 December pass, that money is simply not coming back through this route. This is the most common and most avoidable loss in the whole area, and it is why a taxpayer expecting a refund should treat 31 December as the real deadline rather than a soft one.

Why Section 424 catches people who thought they were fine

Late-filing interest is intuitive: you filed late, so you pay for the delay. Section 424 is not intuitive, and it surprises people every year. It is not a filing penalty at all — it is a charge for having underpaid advance tax during the year, and its clock starts on 1 April of the assessment year regardless of when the due date falls or when you file. If your advance tax and TDS together came to less than 90% of your final assessed tax, it applies. Filing on the very first day of the assessment year would not avoid it; only having paid the tax during the year would have.

That is why the calculator often shows a Section 424 figure even for someone filing on time. In the worked case of a salaried filer with ₹2,00,000 of tax and ₹1,00,000 covered by TDS, filing exactly on 31 July 2026 produces a nil fee, nil late-filing interest, and ₹4,000 of Section 424 interest — four part months from 1 April on the ₹1,00,000 shortfall. Filing earlier would have reduced it; the charge accrues to the date of payment, so paying the balance stops the clock even if the return itself takes a few more days. That is a genuinely useful piece of practical advice and the reverse of what most people assume, which is that nothing can be paid until the return is ready.

Section 424 has a sibling. Section 425 of the Income-tax Act, 2025 (old Section 234C) charges deferment interest where the individual advance tax instalments due on 15 June, 15 September, 15 December and 15 March missed their 15%, 45%, 75% and 100% cumulative targets. Section 425 is fixed by the end of the financial year and is not affected by when you file, so it is not modelled here — but it is a real amount and it stacks on top of everything on this page. Use the advance tax interest calculator for that leg. Where a taxpayer paid nothing at all during the year, the three charges together routinely come to 9% or 10% of the tax liability before the fee is even added.

The cliff at 31 December — a jump, not a slope

The calculator reports what one further month of delay adds, and for most of the year that figure is simply 2% of the unpaid tax — a slope. Around one particular date it is not a slope at all. Crossing 31 December of the assessment year moves the return out of the belated window and into the updated-return regime, where additional tax of 25% of the tax and interest switches on in a single step.

The size of the step is worth seeing. An audit-case filer for FY 2025-26 with ₹3,00,000 of unpaid tax, filing on 20 December 2026, faces a total cost of ₹38,000 — fee, two months of late-filing interest and nine months of Section 424. Filing on 20 January 2027 instead, one month later, costs ₹1,28,750. The extra month adds ₹90,750 where a normal extra month would have added ₹6,000. Nothing about the taxpayer's position changed; a date passed. The calculator flags this explicitly whenever the next month crosses the line, because it is the one moment in the cycle where speed is worth real money and the ordinary intuition — that being a bit later is a bit worse — is badly wrong.

The same shape recurs, less dramatically, at each twelve-month boundary from the end of the assessment year, as the updated-return rate steps from 25% to 50%, then 60%, then 70%. If you are already in updated-return territory, the practical implication is that there is a specific date beyond which your cost rises by a fifth of everything you owe, and it is worth knowing where it is rather than discovering it. And beyond 48 months from the end of the assessment year there is no voluntary route at all — the only way the return gets filed is in response to a notice, with penalty exposure well beyond anything this page computes.

What to do about it, in order

The sequence that minimises cost is not the one most people follow. Pay the tax first, file second. Both interest charges run on the unpaid balance to the date of payment, so paying self-assessment tax today stops roughly 2% a month accruing even if the return itself takes another fortnight to assemble. Many people do the opposite, holding off on payment until the return is complete, and pay for the delay twice over.

Then check the losses. If you have a business or capital loss and the due date has not yet passed, everything else is secondary — file something on time, even an imperfect return, and revise it before 31 December. A revised return preserves the benefit of the original filing date for carry-forward purposes; a belated return does not. This one decision routinely saves more than every other item on this page combined.

Then check whether you are owed a refund. If you are, 31 December is a hard wall, because an updated return cannot claim one. Then work out whether the shortfall that triggered Section 424 will recur next year — if your income has a component that TDS does not reach, such as capital gains, rent, freelance receipts or interest, you are in advance tax territory and the fix is to pay instalments during the year rather than to argue about interest afterwards. Finally, keep the deadline in the calculator's last row somewhere visible. For most of the taxpayers this page is written for, the difference between a costly year and a free one is a single date and about two hours of work.

One caveat on scope. This calculator computes the fee, the two monthly interest legs and the updated-return additional tax, and values forfeited losses at an indicative 30%. It does not model Section 425 deferment interest, penalties for concealment or under-reporting, prosecution exposure for wilful failure to file, or the interest the department owes you on a refund. Where the sums are large, or where a notice has already been received, the numbers here tell you the scale of the problem rather than the whole of it.