TL;DR
September and October 2026 are important compliance months for Indian SMEs and companies. Businesses need to manage GST returns, TDS payments, advance tax, tax-audit requirements, accounting reconciliations and quarterly TDS statements while also preparing for upcoming income-tax and corporate compliance.
For September, businesses should particularly track the 15 September advance-tax instalment, monthly GST filings, TDS payments and the 30 September tax-audit deadline applicable to eligible taxpayers for FY 2025–26. October then brings the Q2 TDS statement deadline of 31 October, along with regular GST and TDS compliance.
A structured compliance checklist can help SMEs and companies avoid late fees, interest, penalties and last-minute reporting errors.
Introduction
September and October are among the busiest compliance months for Indian businesses.
For SMEs, startups, partnership firms and companies, compliance during this period is not limited to GST return filing. Businesses may also need to manage advance tax, TDS/TCS, tax audit, income-tax reporting, accounting reconciliations and other statutory requirements.
The challenge becomes greater when multiple compliance deadlines fall close together. A missed GST filing, incorrect TDS deposit or incomplete tax-audit information can create unnecessary interest, late fees, notices or reconciliation issues.
Businesses should therefore maintain a monthly compliance calendar and complete important reconciliations before the actual filing deadlines.
Here is a practical September–October 2026 business compliance checklist for SMEs and companies.
September 2026 Business Compliance Checklist
1. Review and Pay the Second Advance Tax Instalment
One of the most important September tax deadlines is the second instalment of advance tax.
For taxpayers following the regular instalment schedule, the cumulative advance-tax requirement reaches 45% of the estimated annual advance-tax liability by 15 September.
Before making the payment, businesses should estimate their current-year taxable income and consider:
- Revenue earned so far
- Expected profit for the year
- TDS/TCS credits
- Capital gains
- Other taxable income
- Major business expenses
- Changes in profitability
- Tax already paid
Businesses should avoid simply repeating the previous instalment without reviewing their latest financial position.
2. File GSTR-1 for August 2026
Monthly GST taxpayers generally need to file GSTR-1 for the previous month’s outward supplies by the applicable due date.
GSTR-1 contains important sales and invoice information that subsequently affects GST reporting and recipient-side input tax credit.
Before filing, businesses should verify:
- B2B invoices
- B2C sales
- Credit notes
- Debit notes
- Export invoices
- Amendments
- GSTINs
- Taxable values
- Tax rates
- HSN/SAC information
GSTR-1 is required even where there is no business activity for the relevant tax period, subject to the applicable filing framework.
3. Review GSTR-2B and Input Tax Credit
Before filing the relevant GSTR-3B, businesses should reconcile purchase records with GSTR-2B.
The review should identify:
- Missing purchase invoices
- Incorrect GSTINs
- Duplicate invoices
- Credit notes
- Supplier filing delays
- Ineligible ITC
- Reverse-charge transactions
- Differences between books and GSTR-2B
Businesses should remember that an invoice appearing in GSTR-2B does not by itself establish that every condition for claiming ITC has been satisfied.
4. File GSTR-3B and Pay GST Liability
For monthly filers, GSTR-3B is generally due on the 20th of the following month. The return is used to declare GST liabilities and discharge the applicable tax.
Before filing, businesses should reconcile:
- GSTR-1
- GSTR-2B
- Books of accounts
- Sales register
- Purchase register
- Credit/debit notes
- Reverse charge liability
- GST payments
GSTN also states that GSTR-3B cannot be amended after filing, making pre-filing verification especially important.
5. Deposit TDS for August 2026
Businesses deducting TDS should generally deposit tax deducted during August by 7 September 2026, subject to the applicable exceptions.
The accounting records should be reconciled with:
- TDS payable ledger
- Challans
- Vendor payments
- Salary records
- Professional fees
- Rent
- Commission
- Contractor payments
The Income Tax Department confirms that the general TDS deposit timeline continues to be the 7th of the following month under the current framework.
6. Complete the Tax Audit for FY 2025–26
For businesses covered by tax-audit requirements, September is particularly important.
For FY 2025–26 / AY 2026–27, tax audits continue under the Income Tax Act, 1961. Depending on the circumstances, Form 3CA-3CD or Form 3CB-3CD is applicable.
Businesses should ensure that the auditor has received:
- Final trial balance
- Profit and loss account
- Balance sheet
- Bank statements
- Fixed-asset register
- GST records
- TDS records
- Loan details
- Debtor and creditor details
- Expense ledgers
- MSME information
- Related-party transaction details
- Supporting documents
The tax-audit report deadline for standard cases is 30 September 2026.
7. Reconcile Books With GST
September is a good time to perform a detailed GST-to-books reconciliation.
Businesses should compare:
Sales Register → GSTR-1 → GSTR-3B → Books of Accounts
Differences may arise because of:
- Timing differences
- Credit notes
- Sales returns
- Advances
- Amendments
- Exempt supplies
- Export transactions
- Accounting adjustments
Unexplained differences should be investigated before they become a larger compliance problem.
October 2026 Business Compliance Checklist
8. File the Q2 TDS Statement
The July–September 2026 quarter ends on 30 September.
Businesses deducting TDS should prepare their quarterly TDS statement for Q2.
Under the Income Tax Act, 2025 framework, Form 140 is the quarterly TDS statement for resident non-salary payments, while Form 138 applies to quarterly salary TDS reporting. The Q2 due date is 31 October.
Businesses should reconcile the statement before filing to minimise:
- PAN errors
- Incorrect TDS amounts
- Wrong section reporting
- Challan mismatches
- Duplicate entries
- Incorrect deductee information
9. Reconcile TDS With Books and AIS
After completing the quarter, businesses should compare TDS records with their accounting system.
Check:
- TDS deducted
- TDS deposited
- Vendor-wise deductions
- Salary TDS
- TDS receivable
- TDS payable
- Form 26AS/AIS information
- TDS return data
The objective is to ensure that the amount recorded in the books agrees with the tax actually deducted and deposited.
10. Review October GST Compliance
October continues the regular GST cycle.
Businesses should prepare their sales and purchase data early instead of waiting until the filing deadline.
The monthly GST process should include:
- Finalise sales data
- Reconcile invoices
- Review GSTR-1 data
- Check GSTR-2B
- Reconcile ITC
- Calculate GST liability
- Review reverse charge
- File GSTR-1
- File GSTR-3B
- Preserve filing records
For monthly taxpayers, GSTR-1 is generally due on the 11th and GSTR-3B on the 20th of the following month, subject to applicable rules and extensions.
11. Review TDS Deducted During September
TDS deducted during September generally needs to be deposited by 7 October, subject to applicable exceptions.
Businesses should review all September payments involving potentially taxable categories such as:
- Contractor payments
- Professional fees
- Rent
- Commission
- Interest
- Salary
- Other specified payments
The Income Tax Department confirms that the general TDS deposit timeline remains unchanged under the 2026 rules.
12. Review Outstanding Tax Liabilities
October is a good time to check whether the business has any outstanding:
- GST liabilities
- TDS demands
- Income-tax demands
- Interest
- Late fees
- Outstanding notices
- Previous-period tax balances
Businesses should also review the income-tax e-filing portal for outstanding demands and communications.
Ignoring an old demand or notice can create problems later when filing returns or claiming refunds.
Company Compliance Checklist for September–October 2026
13. Review Statutory Records
Companies should ensure that important corporate records are updated and properly maintained.
Depending on the company’s circumstances, review:
- Board meeting records
- Minutes
- Statutory registers
- Shareholding records
- Director information
- Financial records
- Related-party transactions
- Loans and investments
- Agreements and resolutions
The exact MCA compliance requirements depend on the company’s structure, transactions and applicable provisions.
14. Review Director and Company Details
Companies should verify whether there have been changes in:
- Directors
- Registered office
- Shareholding
- Authorised signatories
- Bank details
- Business activities
- Charges
- Beneficial ownership
Any applicable statutory filing should be completed within its prescribed timeline.
Maintaining accurate master data can also reduce problems during future MCA and tax filings.
15. Review Payroll and Employee Compliance
SMEs should not overlook payroll compliance while focusing on GST and income tax.
Review:
- Salary calculations
- TDS deductions
- Employee reimbursements
- Professional tax where applicable
- Provident fund compliance where applicable
- ESI compliance where applicable
- Leave and payroll records
- Form 16-related records
Payroll records should agree with accounting records and TDS reporting.
October 2026 Income Tax Preparation Checklist
October is also an important month for businesses because audited taxpayers need to move from audit completion toward income-tax return filing.
For FY 2025–26, businesses should ensure that the final tax-audit figures are reconciled with the income-tax return.
Review:
Profit and Loss Account
Check revenue, expenses, depreciation, provisions and tax-sensitive expenses.
Balance Sheet
Verify:
- Debtors
- Creditors
- Loans
- Fixed assets
- Inventory
- Cash
- Bank balances
- Capital
- Reserves
Tax Audit Report
Compare relevant Form 3CD disclosures with the final ITR data.
TDS and TCS
Ensure tax credits claimed in the ITR are supported by available tax records.
GST
Reconcile turnover and other relevant information reported under GST with income-tax records.
Advance Tax
Compare actual advance tax paid with the final estimated tax liability.
Common Compliance Mistakes SMEs Should Avoid
Businesses often face compliance problems because they treat each return separately.
Some of the most common mistakes include:
- Filing GST without reconciling books
- Claiming incorrect ITC
- Missing TDS deposit deadlines
- Filing incorrect TDS statements
- Ignoring AIS/26AS mismatches
- Forgetting advance-tax instalments
- Delaying tax-audit documentation
- Incorrect turnover reporting
- Not maintaining supporting documents
- Ignoring outstanding tax demands
- Mixing old and new Income Tax Act section references
- Leaving company records outdated
- Waiting until the deadline to reconcile financial data
September–October 2026 Compliance Calendar
DateComplianceApplicable To7 September 2026TDS payment for AugustApplicable deductors11 September 2026GSTR-1 for AugustMonthly GST filers13 September 2026IFF for AugustEligible QRMP taxpayers15 September 2026Second advance-tax instalment; cumulative 45%Applicable taxpayers20 September 2026GSTR-3B for AugustMonthly GST filers30 September 2026Tax-audit reportApplicable audited taxpayers7 October 2026TDS payment for SeptemberApplicable deductors11 October 2026GSTR-1 for SeptemberMonthly GST filers20 October 2026GSTR-3B for SeptemberMonthly GST filers31 October 2026Q2 TDS statements for July–SeptemberApplicable deductors
The exact filing requirement can vary based on taxpayer type, return frequency, state, business structure and applicable notifications. GSTN confirms the standard monthly GSTR-1 and GSTR-3B framework, while the Income Tax Department confirms the Q2 TDS statement deadline of 31 October.
How SMEs Can Stay Compliant in 2026
Maintain a Monthly Compliance Calendar
Instead of preparing everything at the end of the month, assign responsibilities for each compliance activity.
Reconcile Before Filing
A simple reconciliation between books, GST, TDS and bank records can identify errors before they become filing problems.
Keep Documents Organised
Maintain invoices, challans, bank statements, agreements, payroll records and tax reports in an easily accessible system.
Track Tax Notices
Regularly check the relevant government portals for notices, demands and communications.
Separate Accounting and Compliance Review
Businesses should ideally review financial records before the final return is filed. A second-level review can identify errors that may otherwise remain unnoticed.
Conclusion
September and October 2026 are critical compliance months for Indian SMEs and companies.
The key priorities include advance tax, GST returns, TDS payments, tax audit, quarterly TDS statements, accounting reconciliations and corporate records.
Businesses should not treat these activities as isolated filings. GST data affects accounting, TDS affects tax credits, tax-audit figures affect the income-tax return and company records support wider statutory compliance.
A well-maintained compliance calendar combined with regular reconciliation can help businesses avoid late fees, interest, penalties and unnecessary notices.
For SMEs and companies, the best strategy is simple: prepare early, reconcile accurately and file on time.
Frequently Asked Questions
1. What are the major business compliance deadlines in September 2026?
Important September deadlines include TDS payment, GSTR-1, the second advance-tax instalment on 15 September, GSTR-3B and the tax-audit deadline on 30 September for applicable taxpayers.
2. What is the advance-tax deadline in September 2026?
The second instalment of advance tax is due on 15 September 2026, with cumulative advance tax generally reaching 45% of the annual liability under the regular instalment schedule.
3. What is the tax-audit deadline for FY 2025–26?
For standard tax-audit cases, the tax-audit report for FY 2025–26 / AY 2026–27 is generally due by 30 September 2026.
4. When is the Q2 TDS return due in October 2026?
The quarterly TDS statement covering July–September 2026 is generally due by 31 October 2026. Under the new Income Tax Act framework, Form 140 covers resident non-salary TDS and Form 138 covers salary TDS.
5. What GST returns are due in September and October?
Monthly GST taxpayers generally need to file GSTR-1 by the 11th and GSTR-3B by the 20th of the following month, subject to applicable rules and extensions.
6. Why should businesses reconcile GSTR-2B before filing GSTR-3B?
GSTR-2B reconciliation helps identify missing invoices, supplier filing issues, duplicate entries, credit notes and potentially ineligible ITC before the business claims credit.
7. What should an SME check before tax audit?
An SME should review turnover, books of accounts, GST reconciliation, TDS/TCS, expenses, depreciation, loans, MSME payments, related-party transactions and supporting documents before finalising the tax audit.
8. Do companies have additional compliance requirements?
Yes. Companies may have additional MCA and corporate-law requirements depending on their structure, transactions, directors, shareholding and other circumstances. Businesses should maintain updated statutory records and track applicable filings separately from tax compliance.
9. What is the biggest compliance mistake SMEs make?
One of the biggest mistakes is waiting until the deadline to prepare and reconcile records. This increases the risk of incorrect returns, missed payments and avoidable interest or penalties.
10. How can businesses manage compliance better in 2026?
Businesses should maintain a central compliance calendar, reconcile books with GST and TDS data every month, monitor tax notices and demands, maintain proper documentation and complete statutory filings before their deadlines.
Blog By : CA Junaid Khan
Written by CA Junaid Ahmed Khan, Junaid Khan & Co., Bhopal.
