IMS becomes mandatory from April 2026 - your 30-day decision rhythm
The Invoice Management System mandate changes ITC monthly. Here's how to set up your firm's 30-day IMS rhythm and the three checks that prevent ITC loss.
IMS mandatory from April 2026 - your 30-day rhythm
The Invoice Management System is now mandatory for every GST taxpayer from 1 April 2026 (CBIC Circular 230/2026-GST). Inward invoices must be accepted / rejected / marked pending in IMS within 30 days. ITC is locked to IMS-accepted invoices.
The 30-day window
- Day 1: Supplier files GSTR-1 → invoice appears in your IMS dashboard.
- Days 2-30: You must act - Accept / Reject / Pending.
- Day 31: Auto-acceptance kicks in. The invoice is treated as accepted; ITC available.
The three actions
- Accept - invoice is correct; ITC flows in.
- Reject - invoice is incorrect (wrong GSTIN, wrong amount, supplier you don't recognise). Rejected invoices don't flow into your ITC.
- Pending - you need time to verify. Treated as "no action" - but if you leave it Pending past day 30, auto-acceptance applies.
The three checks every firm needs
Check 1: Vendor mismatch
Compare IMS invoices against your purchase register. Vendors who file GSTR-1 but you have no PR entry for = potential fraud or duplicate. Reject and notify.Check 2: Amount mismatch
For matched vendors, compare the IMS invoice amount against the PR. Mismatches > ₹100 = supplier filing error or your data entry error. Pending → resolve → Accept or Reject.Check 3: Section 17(5) screen
Even after Accept, screen the invoice against the Section 17(5) blocked-credit list:- Motor vehicles (with exceptions)
- Food & beverages
- Club / health / fitness
- Life / health insurance (personal use)
- Works contract / construction services
- Gifts
Block-flagged invoices: Accept the IMS entry (since the supplier did file), but don't claim ITC in GSTR-3B.
Setting up the rhythm
For a 50-vendor practice:
- IMS check Monday + Thursday - 30 mins each.
- Week-end vendor follow-up - chase suppliers for missing invoices.
- Month-end reconciliation - IMS-accepted vs PR vs GSTR-3B ITC claimed.
For larger firms, automate with the ThynkTax IMS workflow - pulls IMS data daily, auto-categorises, and flags exceptions.
Common questions
Q: What if I miss the 30-day window and the auto-accepted invoice is wrong?
A: You can still reject it later, but the ITC reversal flows in your next GSTR-3B and you may owe interest under Rule 88B if ITC was utilised.
Q: Does IMS apply to ISD?
A: Yes from October 2024. ISD distributions also flow through IMS.
Q: Does IMS affect refunds?
A: Yes. Inverted-duty refunds are now based on IMS-accepted ITC, not 2B.
Cross-references
- ThynkTax workspace: GST IMS
- Circular: CBIC 230/2026-GST
- Statute: Section 16(2)(aa) of CGST Act
- Reviewed by CA Priya Narayanan, Head of GST Practice