Input tax credit made practical: purchase bills, GSTR-2B and the Invoice Management System

Input tax credit (ITC) is the GST you have paid on purchases that you can set off against the GST you collect on sales. For most trading businesses it is the difference between paying GST on their margin and paying it on their entire turnover. Yet small businesses regularly lose credit they were entitled to, not because of any rule, but because of paperwork that arrived late or was never checked.

This guide explains how credit flows today, what the Invoice Management System (IMS) changed, and a simple monthly routine that protects your credit.

How credit flows

The journey of a single purchase invoice looks like this:

1. Your supplier issues the invoice and reports it in their GSTR-1 (or IFF, if they are on the quarterly scheme).
2. The invoice appears in your IMS on the GST portal, where you can act on it.
3. On the 14th of the following month, the portal generates your draft GSTR-2B, a statement of the credit available to you for the month, based on what suppliers reported and the actions you took in IMS.
4. Your GSTR-3B auto-fills the credit from GSTR-2B. You review it, make any reversals required, and file.

The key point is that your credit depends on what your supplier reports, not on the bill in your drawer. If the supplier does not report the invoice, it will not appear in GSTR-2B, and you should not claim it.

Conditions for claiming credit

Under section 16 of the CGST Act, you can claim credit on a purchase only if, broadly:

• you have a valid tax invoice or debit note;
• you have received the goods or services;
• the invoice is reflected in your GSTR-2B;
• the supplier has paid the tax to the government; and
• you have filed your own return.

You must also pay the supplier within 180 days of the invoice date. If you do not, the credit has to be reversed, with interest, until payment is made. And credit for a financial year must be claimed by the time limit in section 16(4), generally 30 November of the following year or the date the annual return is filed, whichever is earlier.

Some purchases never qualify, whatever the paperwork. Section 17(5) blocks credit on items such as most motor vehicles, food and beverages, club memberships and goods for personal use. Ask your accountant which of your regular expenses fall in this list.

The Invoice Management System (IMS)

IMS went live on the GST portal on 1 October 2024. It gives recipients a place to act on each supplier invoice before GSTR-2B is generated. For each record you can choose:

• Accept: the credit moves into "ITC available" in GSTR-2B and flows into GSTR-3B.
• Reject: the credit is excluded. Use this for invoices that are wrong, duplicated or not yours. The supplier sees the rejection and can correct it through GSTR-1A.
• Pending: the record stays in IMS for a later period. Use this when the goods have not arrived yet or the invoice is being checked. Pending records can be held only up to the section 16(4) time limit.

If you take no action, the record is treated as accepted when GSTR-2B is generated. That is convenient, but it means invoices you never looked at can flow straight into your credit. Reviewing IMS before the 14th each month avoids that.

One more dependency: if your previous period's GSTR-3B has not been filed, the portal will not generate the next draft GSTR-2B. Late filing in one month disrupts the next.

Common ways credit is lost

• The supplier files late or not at all. The invoice never appears in your GSTR-2B for the month you expected.
• The wrong GSTIN on the invoice. A supplier who bills your old registration or a branch in another state reports credit that is not available to you.
• Bills that never reach your accountant. Purchase bills sitting in a drawer or a WhatsApp chat are not entered, so nobody notices that the credit is missing.
• Payment beyond 180 days. Credit already claimed has to be reversed.
• Missing the annual time limit for invoices from the previous year.

A monthly checklist

1. Collect every purchase bill for the month in the first week. Photograph them as they arrive rather than at month-end.
2. Check GSTIN, invoice number, date and tax amount on each bill.
3. Before the 14th, review IMS. Accept what matches your bills, reject what is wrong, and keep pending anything you have not yet received.
4. After the 14th, compare GSTR-2B with your purchase register. List bills that are missing from GSTR-2B and the supplier responsible for each.
5. Follow up with those suppliers and ask them to file or correct their GSTR-1. Keep a short list and check it again next month.
6. Before filing GSTR-3B, apply reversals: blocked items, unpaid invoices beyond 180 days, and any other reversal your accountant identifies.
7. Keep the bills organised by month, so that if a scrutiny notice ever asks about a period, the evidence is in one place.

Where an app helps

The most fragile step is the first: getting purchase bills from the shop counter to the accountant. In the SquareBooks business app, an owner photographs a bill as soon as it arrives, and the CA's request for the month's purchase bills appears in the app with a date and a button to scan them. On the firm's side, the bills arrive already attached to the right client and month, ready to review.

Key takeaways

• Your credit follows your supplier's GSTR-1, not the paper bill.
• Use IMS before the 14th: accept, reject or keep pending. No action means deemed acceptance.
• Pay suppliers within 180 days and claim credit within the section 16(4) time limit.
• Collect bills weekly, reconcile with GSTR-2B monthly, and chase missing suppliers.

This guide is general information, not tax advice. ITC rules have conditions and exceptions; confirm your position with your chartered accountant.