GST Registration — Post-Registration Compliance Guide
Once your Goods and Services Tax registration is approved in India, staying compliant is a recurring monthly and annual exercise, not a one-time formality. A regular taxpayer is expected to file outward-supply details, a summary return, and eventually an annual return and reconciliation statement, each on its own statutory clock under the CGST Act and associated rules. Missing any of these deadlines triggers late fees, interest on unpaid tax, and — if lapses continue — a notice from the jurisdictional officer that can escalate toward suspension or cancellation of the GSTIN. This guide walks a newly registered regular taxpayer through the ongoing filing calendar, the common traps that catch first-time filers, and the internal controls that keep the GSTIN in good standing year after year. Rules such as late-fee slabs, turnover thresholds for reconciliation, and QRMP eligibility are periodically revised by the GST Council, so always cross-check the live schedule on the GST portal or with your CA before relying on any specific number below.
Before you start
- Valid GSTIN and registration certificate (Form GST REG-06) issued by the portal
- Login credentials for the authorized signatory on the GST portal
- Digital signature certificate (DSC) or EVC-linked mobile/email for return authentication
- Bookkeeping or accounting software configured to generate GSTR-1/GSTR-3B ready data
- Bank account linked for electronic cash ledger payments
- Vendor invoices and purchase records reconciled against GSTR-2B on a monthly basis
- Decision on QRMP (Quarterly Return Monthly Payment) scheme eligibility if turnover is up to ₹5 crore
- HSN/SAC code mapping for all goods and services supplied, at the mandated digit level
Step-by-step
Confirm your return-filing frequency
Regular taxpayers file GSTR-1 and GSTR-3B either monthly, or quarterly under the QRMP scheme if aggregate turnover in the preceding financial year was up to ₹5 crore. QRMP taxpayers still pay tax monthly via a challan (Form PMT-06) using either the fixed sum or self-assessment method, but file GSTR-1 and GSTR-3B only once a quarter.
Check and, if needed, change your frequency preference on the portal within the window the GST portal opens each quarter — once locked for a quarter it typically cannot be changed mid-cycle.
File GSTR-1 (outward supplies)
GSTR-1 reports invoice-level details of all outward supplies (B2B and B2C). For monthly filers this is generally due by the 11th of the following month; QRMP filers use the IFF (Invoice Furnishing Facility) for the first two months of the quarter and file the full GSTR-1 by the 13th after quarter-end.
- Match invoice numbers, GSTINs, and taxable values against your sales register before submission.
- Amendments to earlier periods can be made in a later GSTR-1, but excess or short reporting causes downstream mismatches in the recipient's GSTR-2B.
Pay tax and file GSTR-3B (summary return)
GSTR-3B is the self-assessed summary return declaring outward tax liability, eligible Input Tax Credit (ITC), and net tax paid through the electronic cash and credit ledgers. Monthly filers generally file by the 20th of the following month; QRMP filers file quarterly by the 22nd or 24th depending on the state group they fall under.
Since the July 2025 tax period, the outward-liability figures auto-populated into GSTR-3B from GSTR-1/IFF are hard-locked and can no longer be edited manually inside GSTR-3B. If the auto-populated figures are wrong, the fix is to amend them in GSTR-1A (or the next GSTR-1) before filing GSTR-3B, not to overwrite the numbers at filing time — confirm the current mechanics on the portal, as this rule is still relatively new.
Even where a monthly tax payment was already made under QRMP, the quarterly GSTR-3B still needs to reconcile that payment against the final liability for the quarter.
Reconcile ITC against GSTR-2B every period
Before claiming ITC in GSTR-3B, reconcile it against the auto-drafted GSTR-2B statement, which reflects invoices your vendors have reported. Only ITC that appears (and is not blocked under Section 17(5)) should be claimed — claiming ITC that a vendor has not uploaded is a common trigger for departmental notices and interest demands.
Track and clear late fees or interest promptly
If a deadline is missed, the portal computes late fees under Section 47 automatically at the time of filing, and interest under Section 50 accrues on any tax paid late. Clearing these promptly — rather than letting them compound across periods — keeps the compliance rating clean and avoids cascading blocks on subsequent filings.
File nil returns even with no activity
GSTR-1 and GSTR-3B must be filed even for a period with zero outward supplies. A simplified NIL filing via SMS is available for GSTR-3B in eligible cases, but the return still has to be submitted — skipping it accrues late fees exactly as a missed regular return would.
Monitor e-invoicing and e-way bill obligations
If your aggregate turnover crosses the notified e-invoicing threshold, B2B invoices must be reported to an Invoice Registration Portal (IRP) to obtain an IRN before they are valid for ITC purposes at the recipient's end. Separately, e-way bills are required for the movement of goods above the prescribed value threshold — confirm current thresholds, as both have been lowered progressively over recent years.
Prepare mid-year books-to-returns reconciliation
Roughly every quarter, reconcile your books of accounts (sales register, purchase register, credit/debit notes) against what has actually been filed in GSTR-1 and GSTR-3B for the corresponding periods. Catching a mismatch mid-year is materially cheaper to fix than discovering it during the annual return.
File the Annual Return — GSTR-9
GSTR-9 consolidates the entire financial year's outward supplies, ITC availed, and tax paid, and is generally due by 31 December following the close of the financial year (i.e., for FY 2025-26, by 31 December 2026, subject to any extension notified). Taxpayers below the notified turnover threshold (historically ₹2 crore) have had the filing made optional in various years — confirm current applicability before assuming exemption.
File GSTR-9C reconciliation statement, if applicable
Where aggregate turnover exceeds the notified threshold (historically ₹5 crore), a reconciliation statement in Form GSTR-9C — reconciling audited financial statements against the annual return — must be filed alongside or after GSTR-9, generally self-certified rather than CA-certified for most taxpayers under current rules. Confirm the applicable threshold and certification requirement for the relevant financial year.
Respond to any notices or discrepancy communications
The department may issue system-generated notices (e.g., Form GSTR-3A for non-filers, or ASMT/DRC series notices for mismatches) if returns are delayed or discrepancies are flagged between GSTR-1, GSTR-3B, and GSTR-2B/2A. Respond within the stated window — an unanswered notice can escalate to best-judgment assessment or suspension of the GSTIN.
Maintain records for the statutory retention period
Retain books of account, invoices, e-way bills, and filed returns for the period prescribed under the CGST Act (generally several years from the due date of the annual return for that year), since these can be called for in audits or assessment proceedings well after the filing itself.
Common mistakes to avoid
- Assuming a nil-activity month does not require filing GSTR-1 or GSTR-3B
- Claiming ITC that has not appeared in GSTR-2B, inviting a mismatch notice
- Missing the QRMP monthly challan payment while assuming quarterly filing means quarterly payment too
- Letting invoice numbering or GSTIN entries diverge between the sales register and GSTR-1
- Ignoring e-invoicing or e-way bill thresholds after turnover crosses the notified limit
- Treating GSTR-9 and GSTR-9C as optional without checking the current turnover threshold
- Delaying resolution of a departmental notice until it escalates to assessment
- Not reconciling books to filed returns until year-end, turning small errors into large ones
- Trying to manually correct the auto-populated liability inside GSTR-3B instead of amending it via GSTR-1A/GSTR-1 before the hard-locked fields are filed
Frequently asked questions
What happens if I miss a GSTR-3B filing deadline?
The portal computes late fees automatically under Section 47 at the time of filing, and interest accrues under Section 50 on any tax paid after the due date. Late fee and interest rates have been revised over time — confirm the current per-day rate and cap on the GST portal or with your CA before assuming a specific figure.
Do I need to file GSTR-3B if there were no supplies in a month?
Yes. A nil return is still mandatory to keep your GSTIN in active, compliant status. A simplified SMS-based nil filing is available for eligible GSTR-3B filers, but skipping the filing entirely accrues late fees the same way a substantive return would.
Who is eligible for quarterly filing under QRMP?
Regular taxpayers with aggregate turnover up to ₹5 crore in the preceding financial year can opt into the QRMP scheme, filing GSTR-1 and GSTR-3B quarterly while still paying tax monthly. Confirm the current turnover threshold, as it is set by notification and can change.
How is late payment interest calculated?
Interest under Section 50 is charged on tax paid after the due date, generally computed on the net cash-ledger liability rather than gross tax, for the number of days of delay. The applicable rate should be confirmed against the current notification before calculating any specific liability.
What is the difference between GSTR-2A and GSTR-2B?
GSTR-2A is a dynamic, real-time statement that updates as vendors file, while GSTR-2B is a static, period-locked statement generated once per return period specifically for ITC reconciliation. Most businesses reconcile ITC claims in GSTR-3B against GSTR-2B because its figures do not change after generation.
Is GSTR-9 mandatory for every registered taxpayer?
Filing has historically been made optional for taxpayers below a notified turnover threshold in several years, while it remains mandatory above it. Because this threshold and the optional-filing notification are reissued periodically, confirm applicability for the specific financial year before deciding not to file.
What triggers a GSTR-9C reconciliation requirement?
GSTR-9C is generally required once aggregate turnover crosses a notified threshold in a financial year, reconciling the annual return figures against audited financial statements. Current rules allow self-certification by the taxpayer in most cases rather than mandatory CA certification, but this should be confirmed for the relevant year.
Can I revise a GST return after filing?
There is no separate revision facility for GSTR-1 or GSTR-3B. Corrections to outward-supply data are made through amendment entries in a subsequent GSTR-1 (or via GSTR-1A before the current period's GSTR-3B is filed), rather than by editing the original filing. Since the July 2025 tax period, the outward-liability fields auto-populated into GSTR-3B are hard-locked and cannot be manually overwritten, so GSTR-1A/GSTR-1 amendment is now the primary correction route rather than adjusting the figure directly in a later GSTR-3B — confirm the current mechanics on the portal.
What happens if I ignore a GST notice?
An unanswered notice — whether a non-filer reminder or a discrepancy notice — can escalate to a best-judgment assessment, additional demand with interest and penalty, and in persistent cases, suspension or cancellation of the GSTIN. Always respond within the window stated on the notice, or seek professional help before the window closes.
How long should I retain GST records?
Books of account, invoices, and filed returns should be retained for the statutory period prescribed under the CGST Act, which runs for several years from the due date of the annual return for that period. Retain records longer than you think necessary, since audit and assessment proceedings can reach back beyond the immediate filing year.
Does my GSTIN get cancelled automatically for repeated non-filing?
Continued non-filing of returns can lead to suo motu suspension and eventual cancellation of registration by the proper officer after due notice under Section 29, though this is not instantaneous and generally follows a series of reminders and a show-cause notice first.
Should I outsource GST compliance to a CA firm?
Once your transaction volume grows or you cross thresholds for e-invoicing, QRMP eligibility, or GSTR-9C, professional support materially reduces the risk of missed deadlines and mismatch notices. Many businesses retain a CA firm on a monthly retainer precisely to keep the recurring filing calendar on track.
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