How to Switch Between Old and New Tax Regime — Rules, Form 10-IEA, and Step-by-Step Process (AY 2026-27)

You know which regime saves you more tax. You have run the numbers, compared the slabs, and made your choice. But now comes the practical question: how do you actually switch?

The process is different depending on whether you earn business or professional income. Get it wrong, and you could lose the ability to switch back entirely. This guide covers the exact steps, the forms involved, and the lock-in rules you need to know for AY 2026-27 (FY 2025-26).

The Default: Everyone Starts on the New Regime

Since AY 2024-25, the new tax regime under Section 115BAC(1A) is the default for every taxpayer in India — salaried employees, freelancers, business owners, and professionals alike. You do not need to file any form or make any declaration to be on the new regime. If you do nothing, you are on it.

This means switching is always about opting out of the new regime and into the old one. And the rules for doing so depend entirely on one question: do you have income under the head "Profits and Gains of Business or Profession"?

Salaried Employees and Investors: Switch Every Year, No Restrictions

If your income comes only from salary, house property, capital gains, and other sources — with no business or professional income — you have maximum flexibility.

How to Switch at Filing Time

You choose your regime while filing your ITR. The income tax portal asks you to select old or new regime before you begin filling in the return. That selection determines which slabs, deductions, and exemptions apply to your computation.

There is no separate form to file. No prior intimation to the department. No lock-in period. You can pick the old regime this year and the new regime next year, and switch back again the year after that. The choice resets every assessment year.

Informing Your Employer During the Year

While the final regime choice is always made at ITR filing, your employer needs to know which regime to use for TDS deductions on your salary during the year. Most employers ask for a declaration at the start of the financial year — typically in April.

Here is what to keep in mind:

• If you do not submit a declaration, your employer will deduct TDS under the new regime (the default)
• If you want TDS under the old regime, submit a declaration to your employer stating your intent to opt out of Section 115BAC
• You can change your mind at filing time — if you told your employer to deduct under old regime but ultimately file under new regime (or vice versa), the TDS difference is adjusted in your return as a refund or balance tax payable

Example: Rajesh asks his employer to deduct TDS under the old regime at the start of FY 2025-26 because he expects to claim Rs 3,50,000 in deductions (80C, 80D, HRA, and home loan interest). His employer deducts lower TDS accordingly. But in March, Rajesh realises his actual deductions are only Rs 1,80,000 because he did not renew his health insurance and his HRA was lower than expected. When he files his ITR, he selects the new regime instead. The excess TDS benefit he received through the year gets adjusted — he pays the balance tax before filing.

Business and Professional Income: The One-Time Lock-In

If you have any income under the head "Profits and Gains of Business or Profession" — whether you are a freelancer, consultant, shopkeeper, doctor, lawyer, chartered accountant, or run a business — different rules apply. This is where Form 10-IEA comes in.

What Is Form 10-IEA?

Form 10-IEA is the form you file on the income tax e-filing portal to formally opt out of the new tax regime when you have business or professional income. Without this form, you cannot claim old regime benefits in your ITR.

The form must be filed on or before the due date of filing your ITR under Section 139(1) — which is July 31 for individuals not subject to tax audit, or October 31 for those who are.

The Lock-In Rule Explained

This is the critical part that trips up many taxpayers. For those with business or professional income, switching is governed by a one-time opt-out, one-time return rule:

In other words, you get exactly one round trip. Once you exercise the option to opt out and then come back to the new regime, the door to the old regime closes permanently for all future assessment years.

Example: Dr. Meera, a consulting physician, files Form 10-IEA for AY 2025-26 to claim deductions under the old regime. For AY 2026-27, she decides the new regime works better (her deductions dropped after she paid off her home loan) and withdraws her Form 10-IEA. She is now back on the new regime. Two years later, she takes a new home loan and wants to switch back to the old regime again — but she cannot. Her one permitted switch-back is already used. She must stay on the new regime for the rest of her career unless the law changes.

When the Lock-In Does NOT Apply

The lock-in rule only kicks in when you have business or professional income. If your income profile changes and you no longer have any business or professional income in a particular year — say you close your practice and join a company as a salaried employee — the lock-in restriction does not apply to that year. You are treated as a salaried taxpayer for that assessment year and can freely choose either regime.

Filing Form 10-IEA: Step-by-Step Process

If you have business income and want to opt for the old regime, here is how to file Form 10-IEA on the income tax portal:

1. Log in to the income tax e-filing portal with your PAN and password
2. Navigate to e-File → Income Tax Forms → File Income Tax Forms
3. Search for Form 10-IEA and select the assessment year (AY 2026-27 for FY 2025-26)
4. Fill in your PAN, name, and the assessment year for which you are opting out
5. Verify and submit using Aadhaar OTP, net banking, or DSC

Important timing: File Form 10-IEA before filing your ITR. If you file your ITR first under the new regime and then try to file Form 10-IEA, the portal may reject it or create complications requiring a revised return.

Common Scenarios and What to Do

"I'm salaried with rental income and capital gains"

No Form 10-IEA needed. Choose your regime at ITR filing time. You can switch every year freely.

"I'm salaried but also do freelance consulting on the side"

Your freelance income counts as business or professional income, even if small. Form 10-IEA rules and the lock-in apply. Consider presumptive taxation under 44ADA to simplify compliance, but note the regime choice still governs your deductions either way.

"I filed Form 10-IEA last year. Do I need to file it again?"

Yes. Form 10-IEA is not a one-time filing. You must file it for each assessment year in which you want to be on the old regime. If you filed it for AY 2025-26 and want the old regime for AY 2026-27 as well, file a fresh Form 10-IEA for AY 2026-27 before the due date.

If you do not file it for a given year, you are automatically on the new regime for that year — and that counts as your "withdrawal," triggering the lock-in rule.

"I already filed my ITR under the wrong regime"

If you filed under the new regime but meant to choose the old regime (or vice versa), you can file a revised return under Section 139(5) before the end of the assessment year (December 31, 2026 for AY 2026-27). For business income earners, make sure your Form 10-IEA status aligns with the regime you are selecting in the revised return.

"My employer deducted TDS under the wrong regime"

This is fixable. The TDS regime used by your employer during the year is not binding — it is a withholding convenience, not a regime election. Your actual regime choice is the one you select while filing your ITR. Any TDS over-deduction or under-deduction gets adjusted through your refund or self-assessment tax payment.

Impact on Advance Tax

Your regime choice affects advance tax calculations because it changes your total liability. Compute advance tax instalments using whichever regime you intend to file under. If you end up switching at filing time, any difference is adjusted as a refund or interest under Sections 234B and 234C.

Strategy: When Switching Makes Sense

The flexibility to switch is most valuable when your financial profile changes year to year. Common triggers:

• Taking or paying off a home loan: The Section 24(b) interest deduction plus 80C principal repayment can tip the balance toward the old regime — and losing them tips it back
• Health insurance changes: A family premium of Rs 50,000–75,000 under Section 80D shifts the calculation
• Children starting college: Tuition fees under 80C and education loan interest under 80E add up
• Changing cities: HRA exemption varies with rent; a move to Mumbai or Delhi can make the old regime worthwhile
• NPS contributions: 80CCD(1B) adds Rs 50,000 in deductions available only under the old regime

Quick Reference: Switching Rules at a Glance

The Bottom Line

For salaried employees without business income, regime switching is effortless — pick the better option each year at filing time. For anyone with business or professional income, the decision carries long-term consequences. Use the old regime only when your deductions clearly exceed the new regime's slab advantage, and avoid casual switching that burns your one permitted round trip.

If you are unsure which regime results in lower tax, 49Tax can compute your liability under both regimes using your actual income and deductions, so you can switch with confidence rather than guesswork.