India Has Two Tax Calendars Right Now. Which One Is Yours?

India has two income tax Acts running at once, and which one governs your return depends not on when you file but on which year the income belongs to.

That sounds like an accountant's problem. It becomes everyone's at the point where it changes the dates — the deadline for a late return is not the same number under the two Acts, and one door closes on 1 April 2026 for good.

Which Act applies to the return I am filing?

The one that governs the year the income was earned, not the year you file. The Income Tax Department's own FAQ is direct about it: "The ITR for income earned during FY 2025-26 will be filed for Assessment Year 2026-27 under the provisions of the Income Tax Act, 1961."

And it pre-empts the obvious objection: "Even though the filing will typically occur after 1st April, 2026 (i.e., after the new Act has come into force), the return relates to a tax year beginning before 1st April, 2026 and is therefore governed entirely by the old Act."

So filing in July 2026 does not put you under the new Act. The old rules, sections and dates follow the income.

One reassurance, because the rumour circulates: you do not have to file twice. Asked whether taxpayers must file for both AY 2026-27 and TY 2026-27 in the transition year, the Department answers simply "No."

What are the late-filing dates under the old Act?

For AY 2026-27, a belated return runs to the end of the calendar year. "Pursuant to Section 139(4) of the Income Tax Act, 1961, a belated return for Assessment Year (AY) 2026–27 may be furnished on or before 31st December 2026, or prior to the completion of the assessment, whichever occurs earlier."

Note the second limb. It is not simply 31 December — it is 31 December or before your assessment is completed, whichever comes first. An assessment completed in October closes the door in October.

The fee is fixed rather than accruing: "in accordance with Section 234F of the Act, a fee for delayed filing shall be levied at ₹1,000 where the total income does not exceed ₹5,00,000, and ₹5,000 in all other cases."

A flat ₹1,000 or ₹5,000, not interest that grows. So under this head, two days late and five months late cost the same — meaning if you have already missed the due date, there is no penalty reason to rush past getting it right.

What changes under the new Act?

The dates stop being calendar dates and become durations. The Department sets out the new limits in Section 263 of the Income Tax Act, 2025:

• Belated return — "Within 9 months from the end of the relevant tax year, or before completion of assessment, whichever is earlier"
• Revised return — "Within 12 * months from the end of the relevant tax year"
• Updated return (ITR-U) — "Within 48 months from the end of the financial year succeeding the relevant tax year"

That asterisk is the Department's own, marking the 12-month figure as "as proposed in the Finance Bill, 2026" — a proposal, not settled law at the time of writing. Treat it as provisional.

The structural change matters: nine months from the end of the tax year is a moving date rather than a fixed 31 December, and four provisions that lived in separate sections are consolidated. The Department describes Section 263 as bringing "original return (sub-section 1), belated return (sub-section 4), revised return (sub-section 5), and updated return (sub-section 6) into one unified section", while "The fundamental structure- mandatory filing, due dates, categories of persons obligated to file-remains the same as that under the old Act."

What closes on 1 April 2026?

Belated and revised returns for older years, permanently. The FAQ is unambiguous: "revised/belated return for AY 2025-26 or an earlier assessment year, cannot be filed after 1st April, 2026."

But not everything closes. "However, a taxpayer may still file his updated return (ITR-U), subject to the time limits prescribed under Section 139(8A) of the old Act."

That is the most useful sentence on the page. The updated return is the long remedy, available "whether or not the person has furnished an original, belated, or revised return", and under the new Act it runs forty-eight months from the end of the financial year succeeding the tax year.

Four years. Most people who assume a missed year is unfixable are wrong — there is a mechanism, it carries additional tax, and it outlasts everything else. The Department's own example has Mr X filing in July 2026, discovering unreported income in January 2028, and still able to file.

Which reminders are worth setting?

Four, and the last one is the one nobody sets:

• Mid-June, every year, to start gathering documents — not to file, but to find what is missing while there is time to chase it.
• A week before your due date, looked up rather than assumed from last year.
• 1 December, every year, if you have missed the due date. Under the old Act this protects the 31 December belated window, and because the fee is flat, what it buys is accuracy rather than speed.
• A one-off, for any year you left unfiled or under-reported. Set it now with the year written in, and check whether the updated-return window is still open. This is the reminder that recovers something; the others only prevent loss.

In ReminderIt you can set these by message — "remind me every year on 15 June to start my tax papers" — and it reads the schedule back before saving.

What this page is not

Tax advice, and no substitute for a chartered accountant — particularly in a transition where two Acts, two sets of section numbers and a live Finance Bill bear on the same filing. Two figures above are marked by the Department itself as proposals.

Your own due date depends on whether your accounts require audit, your category of taxpayer, and extensions the Department sometimes grants. The e-filing portal shows what applies to you.

What the guidance does say plainly: the Act follows the income, not the filing date; the belated fee is flat rather than accruing; belated and revised returns for older years end on 1 April 2026; and the updated return stays open years after everything else has closed.

Source: Income Tax Department, e-filing portal — Income Tax Returns FAQs on the Income Tax Act, 2025: which Act governs AY 2026-27, no double filing in the transition year, the 31 December 2026 belated date and the ₹1,000/₹5,000 fee under section 234F, the Section 263 limits of 9, 12 (proposed) and 48 months, the 1 April 2026 cut-off for older years, and the continued availability of the updated return.