IMS (Invoice Management System) is Now Mandatory Under GST: A Complete Guide

From April 1, 2026, the Invoice Management System on the GST portal is no longer optional. Every regular GST-registered taxpayer who files GSTR-3B must now use IMS to manage inward supplies before filing. If you have been ignoring the IMS tab on the GST portal, that approach will now cost you money.

What is the Invoice Management System?

IMS is a system on the GST portal where supplier invoices, debit notes, and credit notes appear before flowing into your GSTR-2B. You have three choices on each document: Accept, Reject, or mark as Pending. The action you take determines whether that document enters your GSTR-2B and whether you can claim ITC on it.

The Inaction Trap — Critical in 2026

If you take no action on an invoice in IMS before GSTR-2B is generated on the 14th of the month, the system automatically treats it as Accepted. It enters your GSTR-2B without you reviewing it. This means a supplier who filed a wrong invoice of Rs 10,00,000 instead of Rs 10,000 — if you miss it in IMS — will inflate your ITC by Rs 9,90,000. With ITC hard-locking approaching in Phase 2, this inflated figure could get locked into your GSTR-3B as a permanent error.

The Zero Mismatch Policy

From April 2026, the GST portal enforces a hard block on ITC claims where the amount in GSTR-3B exceeds what GSTR-2B shows. This is called the Zero Mismatch Policy. If your claimed ITC is higher than your GSTR-2B, the portal will not let you file GSTR-3B at all. One late-filing supplier can block your entire return. IMS is your first line of defense — by actively managing it, you ensure GSTR-2B reflects only verified, legitimate ITC.

Monthly IMS Checklist

Before the 7th: Log into the GST portal and check which supplier invoices have appeared in IMS. Match these against your purchase records and books of accounts. Before the 11th: Follow up with any supplier whose invoice is missing or incorrect. Request corrections via GSTR-1A from their end. Before the 14th: Complete all Accept, Reject, or Pending actions in IMS. After the 14th, GSTR-2B is generated and actions for that period are locked. After the 14th: Review the GSTR-2B generated. Proceed to file GSTR-3B by the 20th.

What Happens When You Reject an Invoice?

When you reject an invoice in IMS, it does not flow into your GSTR-2B, and you cannot claim ITC on it. The supplier is notified of the rejection and should amend or cancel the invoice through GSTR-1A. Note that the supplier's output tax liability does not reduce simply because you rejected — the supplier still pays tax even if you reject. Coordinate with your supplier to issue a corrected invoice or credit note after rejection.

Who is Exempt from IMS?

Composition scheme taxpayers are not required to use IMS. Import ITC based on the Bill of Entry and ICEGATE data flows directly into GSTR-2B without IMS action. RCM, ISD, and import of services transactions are also outside the scope of IMS.

Disclaimer: Consult your CA for case-specific advice on GST compliance.