Tax Audit Due Date 30 September 2026: AY 2026-27 Checklist + New Form 26 Transition

Last reviewed: 11 September 2026.

Answer first: For AY 2026-27, the Income Tax Department states that the tax-audit report due date is 30 September 2026. This filing belongs to the final assessment-year cycle under the Income-tax Act, 1961. Do not confuse it with Tax Year 2026-27 under the Income-tax Act, 2025: the Department states that the tax-audit report for TY 2026-27 will use new Form 26 and is due on 30 September 2027.

Two dates that should not be mixed up

This transition is important because both cycles can appear in professional work during 2026-27. AY 2026-27 relates to income of the preceding previous-year system, while TY 2026-27 is the first tax year under the new Act commencing from 1 April 2026.

What should be completed before 30 September 2026?

For audit cases falling in the AY 2026-27 cycle, taxpayers and professionals should not treat 30 September as merely an upload date. The audit file should be substantially reconciled before the final week so that the report is supported by books, returns, tax records and documentary evidence.

• Close and reconcile the books of account.
• Match turnover/gross receipts with GST and other relevant reporting.
• Reconcile TDS/TCS, Form 26AS, AIS/TIS and ledger records where applicable.
• Review expense disallowances and statutory-payment issues.
• Check related-party and specified-person reporting requirements.
• Verify fixed assets, depreciation and capital/revenue classification.
• Review loans, deposits, cash transactions and other reportable items.
• Confirm brought-forward losses and relevant deductions.
• Resolve material differences before finalising the audit report.
• Complete auditor/taxpayer portal steps early enough to handle validation or acceptance problems.

Why AY 2026-27 is a transition year

The Income-tax Act, 2025 applies from 1 April 2026, but that does not erase compliance relating to earlier periods governed by the Income-tax Act, 1961. The Income Tax Department's transition guidance confirms that the portal is intended to support old and new form versions simultaneously where required. Professionals therefore need to identify the correct year and law before choosing a form.

New Form 26 for Tax Year 2026-27

The Department's official forms guidance states that the tax-audit report for TY 2026-27 under the Income-tax Act, 2025 will be filed in Form 26 prescribed under the Income-tax Rules, 2026. The Department explains that Form 26 consolidates the erstwhile Forms 3CA, 3CB and 3CD into a unified audit form.

According to the official guidance, the new form rationalises disclosures and aligns reporting more closely with the return framework. It also introduces structured schedules for areas such as losses, depreciation and deductions, prior-period items, computation of receipts/income and computation of expenses. Auditor identification fields include membership number, firm registration number and UDIN.

Old vs new audit-form mapping

The mapping does not mean every old clause has a one-to-one new clause number. The new form has been reorganised, so clause-level mapping should be verified from the notified form and rules rather than inferred from numbering.

Practical audit workflow for September 2026

1. Identify the correct compliance year. Confirm whether the file is AY 2026-27 under the old Act or TY 2026-27 under the new Act.
2. Freeze the accounting data. Avoid repeated late ledger changes without an audit trail.
3. Run reconciliations. Compare books with GST, TDS/TCS, AIS/26AS and other external data.
4. Prepare issue lists. Separate factual mismatches, legal positions, documentation gaps and management confirmations.
5. Clear high-risk items first. Focus on turnover, statutory dues, disallowances, cash/loan transactions and material classification issues.
6. Validate the final report. Check names, PAN, year, audit particulars and portal validation before submission.
7. Preserve evidence. Save working papers, final report, acknowledgement and acceptance/status evidence.

Common transition mistakes

• Using “FY 2026-27”, “AY 2026-27” and “TY 2026-27” as if they are interchangeable.
• Assuming new Form 26 applies to the AY 2026-27 audit due in September 2026.
• Assuming old 3CA/3CB/3CD clause numbering automatically maps one-to-one into Form 26.
• Waiting until the final day to resolve portal or taxpayer-acceptance issues.
• Updating a historical old-law article by merely replacing the year without checking the governing law.

Frequently asked questions

Official source

• Income Tax Department — Income Tax Forms and transition guidance

This article is general professional guidance. Verify the applicable statute, notified form, taxpayer facts and any later CBDT notification/circular before filing.