Filing an income tax return looks simple on the e-filing portal, but small errors made during the process are the most common reason taxpayers receive defective-return notices, delayed refunds, or mismatch communications. For AY 2026-27, which covers income earned during FY 2025-26, the original due date for most non-audit taxpayers was 31 July 2026, so many people are now filing a belated return, which can be submitted until 31 December 2026. That makes accuracy even more important, because a mistake made now cannot always be fixed as cheaply as it could have been before the due date.
The ITR filing mistakes for AY 2026-27 that we see most often include choosing the wrong form, ignoring the Annual Information Statement, leaving out small streams of income, selecting the wrong tax regime, and forgetting to e-verify. This guide explains each of the ten mistakes in plain language, shows how to avoid them, and sets out what to do if you have already made one.
What Are the 10 Most Common Mistakes to Avoid When Filing ITR for AY 2026-27?
The ten most common mistakes are choosing the wrong ITR form, not reconciling AIS and Form 26AS, omitting income, picking the wrong tax regime, claiming unsupported deductions, misreporting capital gains, skipping foreign asset disclosure, entering wrong bank details, not e-verifying on time, and filing late without understanding the consequences. Each one is avoidable with a little preparation.
1. Choosing the Wrong ITR Form
ITR-1 is meant for resident individuals with salary, one house property, and limited other income, and it cannot be used by directors of companies, holders of unlisted equity shares, or people with foreign assets. Capital gains beyond the limited long-term gains allowed under section 112A, business income, or foreign income push you to ITR-2, ITR-3 or ITR-4. Filing in the wrong form usually leads to a defective-return notice under section 139(9).
2. Not Reconciling AIS, TIS and Form 26AS
The Annual Information Statement and Taxpayer Information Summary show interest, dividends, securities transactions and high-value transactions reported to the department by banks, brokers and others. Filing without checking them is the fastest way to create a mismatch. Download all three, compare them with your own records, and explain any difference before submitting.
3. Leaving Out Small or Passive Income
Savings account interest, fixed deposit interest, dividends, rent from a second property, freelance receipts, and gains on mutual funds are frequently forgotten because no one deducted tax on them. All of these are taxable and are usually visible in AIS, so omission is easily detected. Exempt income such as PPF interest should also be reported in the exempt-income schedule.
4. Selecting the Wrong Tax Regime
The new regime under section 115BAC is the default, but taxpayers can still opt for the old regime if it saves more tax. Salaried people can choose each year at filing, whereas those with business income must file Form 10-IEA to opt out of the new regime. Many people compare only the final tax figure and forget that old-regime deductions disappear under the new regime.
5. Claiming Deductions Without Proof or Under the Wrong Regime
Deductions such as section 80C, 80D, HRA, and home loan interest on a self-occupied property are generally available only under the old regime. Claiming them under the new regime, or claiming HRA without rent receipts and the landlord's PAN where required, invites adjustments. Keep every proof on file for several years.
6. Misreporting Capital Gains
Errors arise from using the wrong holding period, mixing short-term and long-term gains, applying the wrong rate, or missing gains on equity-oriented mutual funds, ESOPs and property sales. Always use the broker's capital gains statement and match purchase and sale dates and cost carefully. Gains also affect which ITR form you can use.
7. Ignoring Foreign Assets and Foreign Income
Residents must disclose foreign bank accounts, shares, ESOPs of foreign employers, and other foreign assets in Schedule FA, even if no income arose from them. Non-disclosure can attract a penalty under the Black Money Act of up to ₹10 lakh per default in applicable cases. This is a growing issue for people working with multinational employers.
8. Entering Incorrect or Unvalidated Bank Details
Refunds are credited only to a pre-validated bank account linked to your PAN. A wrong account number, a closed account or a name mismatch can hold up the refund for weeks. Validate the account on the portal and list all savings and current accounts held during the year, except dormant ones as permitted.
9. Forgetting to E-Verify the Return
A return is not treated as validly filed until it is verified, and the portal currently allows 30 days from filing to e-verify through Aadhaar OTP, net banking, or a demat account. Many taxpayers submit the return and assume the job is done. An unverified return is treated as not filed, which can lead to late fees and loss of benefits.
10. Filing Late Without Understanding the Consequences
Missing the due date attracts a late filing fee under section 234F of ₹5,000, reduced to ₹1,000 if total income is up to ₹5 lakh, and interest under section 234A at 1 per cent per month or part of a month on unpaid tax. Business and capital losses generally cannot be carried forward if the return is filed after the due date, though house property loss is an exception. Plan the filing date rather than leaving it to the last moment.
Why Do Mismatches Between AIS, Form 26AS and Your ITR Cause Problems?
Mismatches cause problems because the Income Tax Department compares the figures you declare with the information reported by banks, employers, brokers, registrars and other third parties. When your return shows less income or more TDS credit than that data, the system may flag it for adjustment or enquiry.
| Statement | What it shows | How to use it before filing |
|---|---|---|
| Form 26AS | A tax-credit statement showing TDS, TCS and tax paid | Confirm the tax credit you are entitled to claim in the return |
| AIS | A wider record that also includes savings interest, dividends, mutual fund and share transactions, property purchases and certain high-value spending | Accept correct entries and submit feedback on wrong ones |
| TIS | A summary of the AIS figures by category | Use it for a quick category-wise reconciliation with your own records |
Form 26AS is primarily a tax-credit statement showing TDS, TCS and tax paid, while the AIS is a wider record that also includes savings interest, dividends, mutual fund and share transactions, property purchases and certain high-value spending. The TIS then summarises the AIS figures by category. A common scenario is a salaried taxpayer who has several bank accounts, a few mutual fund redemptions, and dividend income. None of it carries TDS, yet all of it appears in the AIS. If it is left out of the return, an intimation under section 143(1) may propose an adjustment, with tax, interest and sometimes a penalty for under-reported income.
The practical fix is simple. Review the AIS before filing, accept correct entries, and submit feedback on entries that are wrong, for example duplicate reporting or a transaction that belongs to someone else. If you are unsure how to treat an item, a qualified professional can help you decide before the return is submitted. Taxpayers who need support with an assessment or an adjustment proposal can also look at income tax notice handling.
What Happens If You Have Already Made a Mistake in Your ITR?
If you have already made a mistake, you can usually correct it by filing a revised return, responding to a defective-return notice, or, in some cases, filing an updated return. The right route depends on whether the original return was filed on time and how much time has passed.
| Your situation | Route | Deadline and cost |
|---|---|---|
| Return filed on time, but an omission or wrong entry found | Revised return | Window reportedly extended to 31 March 2027 for AY 2026-27 Confirm on portal |
| Return was defective | Response under section 139(9) | Limited period stated in the notice |
| Original due date of 31 July 2026 missed | Belated return | Until 31 December 2026, with late fee under section 234F and interest under section 234A |
| Beyond the belated-return date | Updated return (ITR-U) under section 139(8A) | Until 31 March 2031, with additional tax; cannot be revised once filed Last resort |
A revised return replaces the original and can be filed if you discover an omission or wrong entry. Recent amendments reportedly extended the revised-return window for AY 2026-27 to 31 March 2027, but sources differ, so confirm the current date on the e-filing portal before relying on it. If the return was defective, section 139(9) gives you a limited period to respond with corrected information. If you missed the original due date altogether, you can still file a belated return until 31 December 2026, with a late fee under section 234F and interest under section 234A. Beyond that, an updated return under section 139(8A), known as ITR-U, is available until 31 March 2031, but it carries additional tax and cannot be revised once filed.
Which option is best depends on your facts. For routine form selection and notice-related queries, see our guides on ITR-1 return filing and ITR-2 return filing, or read how the new regime compares with the old regime for AY 2026-27 before deciding which one to file under.
How Has Income Tax Return Filing in India Changed Over the Years?
Income tax return filing in India has moved from paper forms handled manually before 1991 to a data-driven, largely online system in which most information is matched automatically, and the changes explain why many of today's mistakes are caught so quickly.
| Period | Change |
|---|---|
| Before 1991 | Paper returns under the Income-tax Act, 1961, manual assessments and little third-party data to cross-check |
| After 1991 | Gradual computerisation: PAN became central to tracking transactions, TDS expanded, and Form 26AS later brought TDS credits into a single statement |
| Early 2000s | Electronic filing arrived and expanded steadily through the following decade, with e-verification replacing the physical ITR-V in many cases |
| Recent years | Pre-filled returns, the Annual Information Statement and faceless assessment |
| 1 April 2026 | Income-tax Act, 2025 comes into force; returns for AY 2026-27 are still governed by the 1961 Act |
Before 1991, returns under the Income-tax Act, 1961 were filed on paper, assessments were handled manually, and the department had little third-party data to cross-check. After the 1991 liberalisation reforms, the system was gradually computerised: PAN became central to tracking transactions, tax deducted at source was expanded, and Form 26AS later brought TDS credits into a single statement. Electronic filing arrived in the early 2000s and expanded steadily through the following decade, with e-verification replacing the physical ITR-V in many cases.
In recent years the portal introduced pre-filled returns, the Annual Information Statement, and faceless assessment, which together mean that interest, dividends and securities trades reported by third parties are visible to the department before you file. The Income-tax Act, 2025 comes into force from 1 April 2026, but returns for AY 2026-27 are still governed by the 1961 Act. Current forms, utilities and due dates are published on the official portal at https://www.incometax.gov.in.
How Can You Prepare Before Filing Your ITR to Avoid Errors?
You can avoid most errors by gathering your documents, checking the tax statements, choosing the form and regime deliberately, and reviewing the pre-filled data before you submit. A calm half-hour of preparation prevents most notices.
Gather your documents
Start with Form 16 from your employer, bank and deposit interest certificates, capital gains statements, rent receipts and investment proofs.
Download and reconcile Form 26AS, AIS and TIS
Compare all three with your own records before you touch the return, and note every difference you need to explain or correct.
Work out your tax under both regimes
The better option varies from year to year, so compute both. Keep in mind that the section 87A rebate under the new regime can bring tax to nil for lower incomes.
Check the pre-filled data
Review the pre-filled personal, bank and income details instead of accepting them blindly.
Pay any balance tax, then submit
Clear the balance tax before submitting the return, so that interest does not keep running after you have filed.
E-verify straight away
Complete e-verification immediately after submission. An unverified return is treated as not filed.
Taxpayers with business income, foreign assets, or crypto transactions should consider professional help, because the schedules are more detailed; see our pages on ITR-3 return filing, NRI tax filing and filing ITR for cryptocurrency.
