GST Invoice Management System (IMS) Complete Guide for CAs — 2026

What Is IMS and Why GST Moved to Active Reconciliation

Before IMS, GST reconciliation was largely passive: invoices flowed from supplier GSTR-1 into your GSTR-2B, and CAs reconciled mismatches after the fact. ITC was claimed in GSTR-3B without an explicit acceptance step. Disputes between buyer and supplier records were common, and blocked ITC was discovered only at the time of GSTR-9 annual filing.

IMS changes this fundamentally. Every invoice that a supplier files in their GSTR-1 or IFF now appears on the buyer's IMS dashboard before it enters GSTR-2B. The buyer — through their CA — must take one of three explicit actions: Accept, Reject, or Pending. The decision determines whether ITC flows into GSTR-3B.

The ICMAI IMS handbook (December 2025) describes this as the most significant operational change to ITC claiming since the GST rollout in 2017. For CA practices managing multiple GST clients, it means a new monthly workflow step that cannot be skipped.

The Three IMS Actions: What Each Does

Enhanced IMS functionality from 17 October 2025 allows buyers to modify ITC reversal amounts on credit notes. This is relevant when a supplier issues a credit note that partially reverses a prior invoice.

The "Deemed Acceptance" Risk — and Why It Matters

The most dangerous outcome in IMS is not Rejection — it is No Action. If a CA does not log into a client's IMS dashboard and take action before GSTR-3B is filed, every unreviewed invoice is deemed accepted and the ITC flows into GSTR-3B automatically.

This creates three real risks:

• Invalid ITC claimed: If a supplier uploaded a fake, duplicate, or incorrect invoice and you did not reject it, the ITC is deemed claimed by you. GST notices for wrongful ITC follow.
• Blocked ITC not flagged: If you intended to dispute an invoice (goods not received, wrong amount), silence means you have accepted. Reversing it later requires a manual amendment and interest payment.
• Ineligible ITC flowing through: Invoices for personal use, non-business expenses, or blocked categories (Section 17(5)) that the CA should have rejected will auto-populate into GSTR-3B Table 4(A) if left unactioned.

The fix is simple: build IMS review into your monthly GST workflow, before GSTR-3B filing — not after.

56th GST Council Rate Changes: Two-Tier Structure

The 56th GST Council (3 September 2025) announced a significant rate rationalisation: the 12% slab is eliminated, and most goods in the 28% slab move down. The result is an effective two-tier system of 5% and 18% for most goods. Sin goods (tobacco, aerated beverages, luxury items) retain their old rates. Changes took effect on 22 September 2025 for most items and 1 November 2025 for phased categories.

CAs advising trading or manufacturing clients should verify the specific HSN code rate applicability from the official CBIC rate schedule. The above is a summary of major category changes.

Monthly IMS Processing Checklist for CAs (8 Steps)

Run this checklist for each GST-registered client before their GSTR-3B filing date. For monthly filers, this is the 20th of each month. For QRMP filers, it is the last date of the quarter.

1. Log into GST portal on behalf of client (as authorised signatory or via DSC) and navigate to Services → Returns → Invoice Management System.
2. Download the IMS dashboard export as CSV/Excel. Sort by supplier GSTIN to cross-check against your client's purchase register.
3. Match each invoice to client's purchase register. Flag invoices that do not match any purchase order or GRN (goods receipt note).
4. Identify ineligible ITC invoices — personal use, blocked categories u/s 17(5) (motor vehicles, food, club memberships, works contract for immovable property, etc.). Mark these for Rejection.
5. Check credit notes. Use the enhanced IMS functionality (from 17 Oct 2025) to adjust ITC reversal amounts if the credit note partially reverses a prior invoice.
6. Action all reviewed invoices: Accept valid invoices, Reject ineligible or incorrect ones, mark Pending only where supplier clarification is genuinely awaited (and only if within the 1 period / 1 quarter window).
7. Verify GSTR-2B after IMS actions are saved. Confirm the ITC Available section matches your client's expected ITC before filing GSTR-3B.
8. Document your IMS decisions. For rejected invoices, note the reason (goods not received, wrong amount, ineligible category). This becomes your defence in a future GST audit.

How Glomiq Helps CAs With GST Documentation

IMS creates documentation obligations that did not exist under the old passive GSTR-2B system. Every month, CAs need to produce:

• ITC reconciliation reports (what was accepted, what was rejected, what is pending and why)
• Client advisory letters explaining rate changes under the 56th Council
• GSTR-3B cover letters summarising ITC claimed and adjustments made
• GST engagement letters with updated scope that now includes IMS management

Glomiq lets you build these as templates once and generate client-specific versions in under 2 minutes. Upload your existing ITC reconciliation report format, define the variable fields (client name, GSTIN, period, ITC figures, notes on rejections), and generate 30 client reports in the time it previously took to write one.

CA Anal Shah of Patan reduced her monthly GST documentation time by 80% using Glomiq — “I fill a form and download in under 2 minutes. The formatting stays perfect — no more reformatting after every edit.”

Frequently Asked Questions

What happens if I miss the IMS window and GSTR-3B is filed with auto-accepted ITC?

Once GSTR-3B is filed, the ITC is deemed claimed. To reverse wrongly claimed ITC, you must file a manual amendment in the next period's GSTR-3B (Table 4(B) — Ineligible ITC) and pay interest at 18% per annum on the reversed amount from the date of the original claim. This is why proactive IMS review before filing is essential — reversals after the fact are expensive.

My client is a QRMP filer. How does IMS work for them?

QRMP (Quarterly Return Monthly Payment) filers file GSTR-1 quarterly but pay tax monthly via PMT-06. For IMS, they have a broader window: invoices can remain in Pending status for up to one full quarter before they must be actioned. The IMS review should happen before the QRMP quarterly GSTR-1/IFF filing deadline. Accept decisions flow into the quarterly GSTR-2B and then GSTR-3B.

Does IMS affect the way credit notes from suppliers are handled?

Yes. From October 2025, IMS includes enhanced functionality for credit notes: you can now view supplier credit notes on the IMS dashboard and modify the ITC reversal amount before it feeds into GSTR-2B. This is particularly important when a supplier issues a partial credit note — under the old system, the full credit note amount automatically reduced GSTR-2B ITC. Now the CA can adjust the reversal to match the actual situation.