GST and income tax are separate systems, so there is no single “GST ITR” return or universal due date. GST returns report indirect-tax transactions, while an income tax return (ITR) reports annual income, deductions, tax liability, and other disclosures. A business may need to meet both calendars, often using overlapping books and invoices.
Due dates can change through government notifications, and some GST deadlines vary by state, turnover, return type, or notification. Treat the dates below as the standard framework for planning in 2026, then verify the final deadline on the official GST portal and the Income Tax e-Filing portal before filing.
GST and ITR: what each filing covers
GST filings generally capture outward supplies, tax collected, eligible input tax credit (ITC), reverse-charge transactions, and payment of net tax. Common forms include GSTR-1, GSTR-3B, CMP-08, GSTR-4, GSTR-9, and GSTR-9C where applicable.
ITR filings report income under relevant heads, advance tax and tax deducted at source, deductions, foreign assets or income where applicable, and final tax payable or refundable. The correct ITR form depends on the taxpayer’s status, income sources, turnover, and other conditions.
A GST registration does not automatically determine the ITR form. For example, a sole proprietor generally files an individual ITR, while a company files a corporate return. Keep this distinction clear when creating a compliance calendar.
Standard GST due dates
The following are the usual statutory deadlines, subject to notifications and taxpayer-specific rules:
- GSTR-1, monthly filers: 11th of the following month.
- GSTR-1, quarterly filers under QRMP: 13th of the month following the quarter, unless a different mechanism or notification applies.
- GSTR-3B, monthly filers: 20th of the following month.
- GSTR-3B, quarterly filers under QRMP: generally the 22nd or 24th of the month following the quarter, depending on the state or Union territory.
- PMT-06 under QRMP: generally by the 25th of the month following the first two months of a quarter.
- CMP-08 for composition taxpayers: 18th of the month following each quarter.
- GSTR-4 for composition taxpayers: annual return, generally due by 30 April following the financial year, subject to applicable rules and notifications.
- GSTR-9 and GSTR-9C: generally due by 31 December following the relevant financial year, where the taxpayer is required to file them.
The portal may show the due date applicable to your registration. Do not assume that a missed GSTR-1 deadline can be ignored because GSTR-3B was filed: invoice reporting and tax payment are related but separate obligations.
Standard ITR due dates
For a financial year ending 31 March, the assessment year follows it. The commonly applicable ITR framework is:
- 31 July: individuals and HUFs not requiring audit, subject to the notified deadline.
- 30 September: taxpayers whose accounts require audit, where this is the applicable statutory deadline.
- 31 October: taxpayers required to furnish a transfer-pricing report, where applicable.
- 30 November: certain companies and taxpayers with international or specified domestic transactions covered by transfer-pricing provisions.
- Belated return: generally permitted after the original due date until the statutory cut-off notified for that assessment year, with applicable late fee and interest.
These dates are not a substitute for checking the relevant year’s notification. Tax audit reports, transfer-pricing reports, revised returns, updated returns, advance-tax instalments, and tax-payment deadlines follow their own rules.
Late fees, interest, and practical consequences
Late filing can create more than a one-time penalty. Depending on the form and circumstances, you may face:
- GST late fees for delayed returns, subject to statutory caps, waivers, and conditional relief announced by the government.
- Interest on delayed GST tax payment, generally calculated on the unpaid tax for the relevant period.
- Income-tax late fee under section 234F, where applicable, based on total income and the timing of filing.
- Interest under sections such as 234A, 234B, or 234C, depending on the nature of the shortfall or delay.
- Blocked or delayed compliance actions, including difficulties with refunds, notices, tenders, loans, or vendor onboarding.
Late filing does not automatically mean that every ITC claim is lost, nor does filing on time guarantee that every credit is admissible. Match purchase records, supplier filings, tax invoices, payment conditions, and other eligibility requirements before claiming ITC.
A practical monthly and annual workflow
Builders, agencies, SaaS companies, and other growing businesses should treat compliance as an operating process rather than an annual scramble. A workable workflow is:
1. Close the books quickly: reconcile bank entries, sales invoices, credit notes, expenses, payroll, and advances.
2. Separate GST data: classify taxable, exempt, nil-rated, export, reverse-charge, and out-of-scope transactions.
3. Reconcile outward supplies: compare the sales register with GSTR-1 and resolve cancelled or amended invoices.
4. Validate ITC: compare purchase records with available statement data, remove ineligible credits, and document reversals.
5. Calculate cash requirements: estimate GST payment, TDS, advance tax, and income-tax liability before the deadline week.
6. Review before submission: check place of supply, GSTIN, HSN or SAC, tax rates, amendments, and bank details.
7. Save evidence: retain filed forms, challans, reconciliation workpapers, invoices, and acknowledgement numbers.
Use a calendar with separate columns for period, form, data owner, reviewer, payment date, filing date, and acknowledgement. Automated reminders can help, but software does not replace review. Teams handling high-volume customer queries may also evaluate automated user feedback categorization for Indian SaaS to route compliance-product issues to the right owner.
What to do after missing a deadline
Do not wait for the next notice. First identify the missed form, tax period, unpaid tax, and whether a return is still pending or can be amended. File the earliest permissible return, pay tax and applicable interest, and calculate late fees using the portal or professional advice. Reconcile the period afterward because a late filing can expose errors in sales, ITC, or liability reporting.
If the delay was caused by a portal outage, disaster, or an officially recognised issue, preserve screenshots, error messages, helpdesk tickets, and timestamps. Relief is available only when formally notified; an informal assumption that the portal was slow is not a compliance defence.
Filing checklist for 2026
Before each submission, confirm:
- The correct GST return and ITR form has been selected.
- Books, invoices, bank records, and tax statements are reconciled.
- GST liability and ITC are supported by records.
- TDS, advance tax, and self-assessment tax credits are correctly reflected.
- Digital signature, electronic verification, or authorised signatory access works.
- Payment challans and acknowledgements are saved.
- Any notice, mismatch, refund, or defective-return communication has an owner and deadline.
Finally, revisit the calendar whenever the GST Council, Central Board of Direct Taxes, or portal issues a notification. For founders building compliance-heavy products, India’s wider AI ecosystem—including Indian open-source AI developer projects—can offer useful examples of automation, but tax decisions should remain reviewable, documented, and accountable.