The Month-End GST Reconciliation Workflow: A Step-by-Step Close Checklist for CA Firms
Monthly GST close is not one reconciliation but four, run in a specific order against deadlines that no longer forgive a late catch. This is the sequence a firm can standardise across every client and every GSTIN.
A GST month-end close done well is boring. The same steps, in the same order, against the same calendar, for every client. It is the firms that improvise each month — chasing whichever return is closest to its deadline — that end up with mismatches carried forward, Rule 88C intimations, and a GSTR-9C that takes three weeks. With hard-locking and IMS now in force, the improvised approach has stopped being merely inefficient; it produces returns that cannot be corrected after filing.
The close is four reconciliations, and the order matters because each one feeds the next.
Step 1 — GSTR-1 against the sales register (by the 10th)
Before GSTR-1 is filed, every outward-supply table should tie to the books: B2B and B2CL invoice-by-invoice, B2CS in summary by rate and place of supply, credit and debit notes against the correct original invoices, and the HSN summary reconciled to total turnover. Because Tables 3.1 and 3.2 of GSTR-3B are now locked to this filing, an error that survives this step becomes an error you cannot fix in GSTR-3B — only through GSTR-1A within a narrow window, or a later amendment on record.
- Match invoice count and total taxable value between the register and the draft GSTR-1.
- Confirm every amendment made this month is tagged to the period it corrects, not the current one.
- Reconcile export and SEZ invoices separately — LUT status, shipping bill details, and zero-rating basis.
- Resolve every difference before filing. File GSTR-1A in the same period if something is found after GSTR-1 but before GSTR-3B.
Step 2 — IMS dashboard review (before the 14th)
Between the GSTR-1 cut-off and GSTR-2B generation on the 14th, every supplier invoice sitting in the IMS dashboard needs a decision. Accept what matches a real purchase, reject what does not belong to the entity or is materially wrong, and leave genuinely uncertain items pending — but track the pending list, because an invoice left pending indefinitely is credit deferred and, past the Section 16(4) window, credit lost.
Step 3 — GSTR-2B against the purchase register (by the 18th)
Once GSTR-2B is generated, reconcile it against the purchase register on three levels: presence (is the invoice in both), value (do taxable value and each tax head agree on matched lines), and eligibility (is anything in the 2B's ITC Not Available section, and does any matched-and-available invoice fall under Section 17(5)). Everything in the register but not the 2B goes on a supplier follow-up list. Everything in the 2B but not the register is a missed purchase entry or a wrong-GSTIN invoice that should have been rejected in IMS.
| Situation | Likely cause | Action this month |
|---|---|---|
| In register, in 2B, values agree | Clean match | Claim the credit |
| In register, in 2B, values differ | Data entry error one side, or supplier reported wrong amount | Correct the register or raise with supplier; claim only the 2B value |
| In register, not in 2B | Supplier filed late or not at all, or you rejected it in IMS | Defer the claim; add to supplier follow-up; check IMS status |
| Not in register, in 2B | Missed purchase entry, or invoice wrongly issued to your GSTIN | Book the purchase, or reject in IMS before 2B finalises |
| In 2B, ITC Not Available section | Place of supply, supplier beyond 16(4), composition supplier | Do not claim; document the reason |
Step 4 — GSTR-1 against GSTR-3B, then file (by the 20th)
Immediately before filing GSTR-3B, reconcile the outward liability tax-head by tax-head (CGST, SGST, IGST, cess) against the GSTR-1 already filed, and separately track any GSTR-1 amendments this month against the original period they correct. Confirm the ITC figure equals the reconciled GSTR-2B number from Step 3 and does not exceed the auto-populated balance. At this point GSTR-3B should be a verification, not a calculation — if a number is a surprise here, an earlier step was skipped.
Standardising it across the firm
The leverage is not a cleverer checklist — it is running the identical process for every client and every GSTIN, so a discrepancy is caught by the same logic everywhere rather than depending on which associate handled which client that month. Two things make that possible: a fixed internal calendar keyed to the 10th, 14th, 18th and 20th, and a single data-extraction method so the source sheets look the same for every entity.
GST Reco Pro converts GSTR-1 and GSTR-3B PDFs — up to 24 per batch, mixed across return types — into consistent, column-matched Excel sheets in the browser, with nothing uploaded. It is the piece that lets one reconciliation template run unchanged across an entire client book.
Standardise your GSTR data extraction →Related reading: standardising reconciliation across branches and states when one client has many GSTINs.
Read the multi-GSTIN reconciliation framework →Frequently Asked Questions
In what order should monthly GST reconciliation be done?
GSTR-1 against the sales register before filing GSTR-1; the IMS dashboard before GSTR-2B is generated on the 14th; GSTR-2B against the purchase register once it is generated; and finally GSTR-1 against GSTR-3B tax-head by tax-head immediately before filing GSTR-3B.
What is the deadline for reviewing the IMS dashboard each month?
Before GSTR-2B is generated, which is the 14th of the following month for monthly filers. Invoices not actioned by then are deemed accepted and flow into GSTR-2B as available credit.
Why reconcile GSTR-1 with GSTR-3B before filing rather than after?
Because a mismatch between outward supplies in GSTR-1 and tax paid in GSTR-3B can trigger a Rule 88C intimation within days, and with GSTR-3B fields now locked to GSTR-1, a difference found after filing costs a full amendment cycle instead of a quick correction.
How can a CA firm standardise GST close across many clients?
Fix an internal calendar to the key portal dates (10th, 14th, 18th, 20th), use one reconciliation template for every entity, and standardise how return data is extracted so every client's working sheets have the same structure and the same matching logic applies everywhere.
What should be treated as the output of a monthly GST close?
A filed GSTR-1 and GSTR-3B that tie to each other and to the books, a cleared or documented IMS dashboard, a GSTR-2B reconciliation with every exception assigned an action, and a short working-paper file that would let someone reconstruct every ITC and liability figure if a notice arrives.