If you've received a notice under Section 148 of the Income Tax Act, the first instinct is usually panic. Your return was already filed, maybe even years ago, and now the department wants to look at it again. Take a breath  a reassessment notice is not automatically a penalty or an accusation. It simply means the Assessing Officer (AO) has information suggesting that some income wasn't fully assessed the first time around, and the law gives you a fair chance to explain before anything is finalised.

This year, a lot of taxpayers are seeing these notices land in their inbox, partly because the transition to the Income Tax Act, 2025 means the department is closing out older cases under the earlier law before the new provisions fully take over. Here's what Section 148 actually means, why it's showing up now, and exactly what you need to do.

What Is Section 148, Really?

Section 147 of the Income Tax Act, 1961 gives the department the power to reopen and reassess a previously filed return. Section 148 is the notice that formally kicks off that process  it asks you to file your return again for that assessment year, even if you already filed it or the assessment was closed.

A Section 148 notice can't just land on your desk out of nowhere. Since the Finance Act 2021, the AO must first go through a safeguard step under Section 148A  conduct an inquiry, issue a show-cause notice, share the information relied upon, and give you a real opportunity to respond, before deciding whether a full Section 148 notice is even warranted.

Why Are So Many Notices Going Out Right Now

Two things are converging in 2026, and it's worth understanding both.

1. The Income Tax Act, 2025 transition

The new Income Tax Act, 2025 came into effect on 1st April 2026, but it doesn't wipe the slate clean on pending matters. Section 536(2)(c) of the new Act makes clear that provisions of the repealed 1961 Act continue to apply to any proceeding that was already pending when the new Act commenced. In practical terms, that means reassessment proceedings starting under a Section 148A notice for older years, including their eventual Section 148 notice, are still governed entirely by the old 1961 Act framework  deadlines, approval hierarchy, and the ITR form to be used all follow the earlier rules.

The department is effectively racing the clock on older assessment years before the corresponding old-Act deadlines close out for good, which explains the wave of notices for AY 2022-23, 2023-24, and 2024-25 you may be hearing about.

2. Better data matching by CBDT

The department increasingly relies on automated risk flags  mismatches between your ITR and data available through AIS, TDS/TCS statements, high-value transaction reporting, and third-party information. If your bank deposits, property transactions, or capital gains don't line up with what you declared, that mismatch alone can trigger a Section 148A inquiry.

Common Reasons You Might Get a Notice

• Unreported income: freelance earnings, rental income, or interest income missing from your ITR.
• Unexplained cash deposits or high-value transactions: large bank deposits that don't match your declared income.
• Property or capital gains mismatches: sale or purchase of property, shares, or mutual funds not reflected correctly.
• TDS/AIS mismatches: income reported by a deductor or third party that doesn't appear in your return.
• Information from other agencies: data shared by banks, registrars, or other government departments pointing to possible tax evasion.

Time Limits You Should Know

These limits apply to notices issued on or after 1 September 2024; notices issued earlier follow the older timeline. If a notice lands outside this window, its validity itself can be challenged — this has been the basis for several successful appeals before the Income Tax Appellate Tribunal.

How to Respond — Step by Step

1. Don't ignore it. If you don't respond, the AO can proceed with a "best judgment" assessment under Section 144, using only the information available to them — usually not in your favour.
2. Read the reasons carefully. The Section 148A show-cause notice must set out the information the department is relying on. If it isn't clear, you're entitled to ask for it.
3. Check the timeline. Confirm the notice falls within the applicable limitation period for that assessment year.
4. Gather your documents. ITR acknowledgment, Form 26AS, AIS, bank statements, and source-of-funds proof for any flagged transaction (sale deeds, gift deeds, FD receipts, broker statements).
5. File a considered response. Address each point raised  don't just resubmit your old return without explanation.
6. Get professional help. A CA can assess whether the notice itself is procedurally valid before you even get into the merits of the case.

What Happens If the Reassessment Goes Ahead

If, after your response, the AO decides to proceed, you'll need to file a fresh return for that assessment year within the time mentioned in the notice. If additions are made to your income and you disagree, you can appeal to the Commissioner of Income Tax (Appeals) or the Income Tax Appellate Tribunal. You can also challenge the validity of the notice itself in the High Court through a writ petition, even before the reassessment concludes.

Bottom Line

A Section 148 notice is a process, not a verdict. The law builds in real safeguards  the 148A inquiry, defined time limits, and approval requirements  precisely so reassessment isn't triggered casually. The best move is to respond on time, with proper documentation, ideally with a tax professional reviewing both the notice's validity and your explanation before you submit it.