Quick context: The new regime has been the default since FY 2023-24. That single change is what makes this question expensive — the choice now happens whether or not you make it, and the deadline that governs it is the one under section 139(1), not the belated-return window.
A lot of people work out that the old regime would have suited them better only after their employer has deducted TDS all year on the new one, or after they have already filed.
Whether that can be fixed depends entirely on where you are standing when you ask. There are four positions, and they have four different answers. Most of the confusion online comes from articles that answer one of them and imply it covers all four.
# 1. You have not filed yet, and you are salaried
The easy case. If you have no business or professional income, you may choose either regime every single year, directly in the return, with no separate form and no carry-over of last year's choice.
Run both computations on your actual numbers and take the lower one. The income tax calculator does both side by side; if you want the reasoning rather than the number, the old vs new regime decision guide works through where the crossover actually falls.
# 2. You have not filed yet, and you have business or professional income
Stricter, and the strictness is the point. The new regime is the default here too, so choosing the old one means actively opting out — and that is what Form 10-IEA does.
It must be filed on or before your due date under section 139(1). Not with the return, before or with it, but not after.
And the withdrawal rule is the one to read twice. The statute allows the option, once exercised, to be withdrawn only once — and after that withdrawal the person is never again eligible to exercise it, for as long as the business or professional income continues.
That is close to a one-way door. Compare both regimes properly before submitting Form 10-IEA, because undoing it later is far more restrictive than anything a salaried filer faces.
# 3. The due date has passed and you have not filed at all
This is the one most people have backwards, including several articles currently ranking for this query.
The common claim is that a belated return locks you out of the new regime. It is the other way round. On a belated return you lose the old regime and are left in the new one.
Here is why, and it is worth following because the logic settles every version of this question:
- The new regime is the default. You do not opt into it; you are in it unless you opt out.
- The right to opt out is exercised along with the return furnished under section 139(1) — the return filed by the due date.
- A belated return is furnished under section 139(4), not 139(1).
- So the opt-out cannot be exercised, and the default stands.
The practical consequence is the opposite of the usual warning. If the old regime is better for you — substantial HRA, a home loan, a full 80C, senior-citizen parents under 80D — then missing the due date does not merely cost you the ₹5,000 late fee under section 234F. It costs you the entire difference between the two regimes for that year, and no revised return brings it back.
If the new regime was going to be better for you anyway, filing late costs you the late fee and nothing more on this front.
So the deadline matters asymmetrically, and it matters most to exactly the people who most often assume they have time. Check your ITR due date — they are staggered by category and not everyone has the date they think they do.
# 4. You filed within the due date, and picked the wrong one
Here the honest answer is that it is not settled, and pretending otherwise would not serve you.
The statute ties the option to the return furnished under section 139(1). The question is whether a revised return under section 139(5) steps into the shoes of that original return for this purpose, or whether the choice was fixed the moment the original was filed.
Established tax platforms take opposite positions on this, in their own published guidance, as at the time of writing. That divergence is itself the finding: it is not a rule you should resolve by picking whichever page you found first.
If you are in this position — salaried, filed on time, want to switch — get it looked at against your own facts before you plan around either answer. The cost of being wrong is not just the tax; it is a revised return being questioned after you have already spent the refund you expected.
# The whole thing in five lines
| Where you are | What happens |
|---|---|
| Not filed, salaried | Pick either regime freely, every year, no form |
| Not filed, business income, want old | Form 10-IEA before the s.139(1) due date |
| Filed on time, want to switch | Genuinely unsettled — get it reviewed on your facts |
| Due date passed, not filed | You keep the new regime and lose the old |
| Business income, already withdrawn once | Effectively final while the business income continues |
On the Income-tax Act 2025. The provision governing the new regime is renumbered under the 2025 Act, and the mechanics of exercising the option may look different for tax years from 2026-27 onward. That does not affect the return most people are filing now for FY 2025-26. We are not printing a new section number here that we have not verified against the bare Act — our section mapping cheat sheet is the place we keep those, and several mappings circulating online are wrong.
# Why this turns into a notice
A regime switch handled loosely is one of the tidier routes to a mismatch. The employer deducted TDS on one basis, the return was filed on another, and the Form 26AS and AIS figures no longer line up with the computation. That is a s.143(1) adjustment waiting to happen — and it arrives months later, when the reasoning is hard to reconstruct. If one has already landed, the notice response framework sets out what each type actually requires.
Compare both regimes on your real numbers, with a CA reviewing the return before it is submitted. Start free →
# Related reading
- Old vs new tax regime — the decision guide
- ITR due dates AY 2026-27 — who actually gets which date
- Income tax notice response framework
Disclaimer: This article explains general rules and is not a substitute for advice on your own facts. The position on whether a revised return can change an already-filed salaried return's regime choice genuinely differs across established sources as at the time of writing, and is flagged as unsettled above rather than resolved. Confirm your situation with a qualified Chartered Accountant before acting. Data verified 5 September 2026.
