Staying compliant with GST doesn't require mastering every provision — but it does require knowing exactly which return is due, on which date, and with what data. One missed deadline can trigger late fees, interest at 18% per annum, and in the worst cases, suspension of your GSTIN. This calendar is the one document your finance team needs on the wall for 2026.
Monthly return filers: your core calendar
If your aggregate turnover exceeded ₹5 crore in the previous financial year, you are a mandatory monthly filer. The three returns that govern your life are GSTR-1 (outward supplies), GSTR-3B (summary return and payment), and for recipients, GSTR-2B (auto-populated ITC statement). The 11th is GSTR-1's due date, the 20th is GSTR-3B's. Do not miss the 11th — errors corrected after the 10th affect your counterparty's ITC, and disputes follow.
Quarterly filers (QRMP scheme, turnover under ₹5 crore) submit GSTR-1 quarterly but pay tax monthly via PMT-06 challan. The 25th of each month is your payment date; GSTR-3B is filed quarterly by the 22nd (Category I states) or 24th (Category II states) of the month following the quarter. Getting these mixed up is one of the most common errors we see.
Key date: The due date for GSTR-9 (annual return) and GSTR-9C (reconciliation statement) for FY 2025-26 is 31 December 2026. Block time in your calendar now — the preparation typically takes 4–6 weeks for a business with multiple state registrations.
Annual and one-time filings
GSTR-9 is mandatory for every taxpayer with aggregate turnover above ₹2 crore. Below that threshold, filing is optional but strongly recommended — the annual return is the only place where ITC mismatches from the full year can be reconciled cleanly, before the department raises a notice. GSTR-9C (reconciliation statement with auditor certification) is required for turnovers above ₹5 crore.
The ITC reconciliation window
Section 16(4) limits input tax credit claims to the earlier of the date of filing the annual return or 30 November of the following financial year. For FY 2025-26 credits, this means any unclaimed ITC must be claimed by 30 November 2026 in your October 2026 GSTR-3B. A reconciliation exercise in July–August is advisable to identify any credits sitting in GSTR-2B that were not claimed in the monthly returns.
What triggers notices
The GST portal's risk-scoring engine cross-matches GSTR-1, GSTR-3B, and GSTR-2B automatically. Common triggers: ITC claimed in 3B that exceeds 2B (over-claim), turnover reported lower in 3B than in 1 (under-declaration), and e-invoice non-compliance for businesses above ₹5 crore turnover. A clean reconciliation before filing eliminates most of these risks before they become notices.
If you need help building a compliance calendar tailored to your state and turnover bracket, speak to our GST team — we prepare these for clients as part of every engagement kick-off.
