Section 16(2)(c) has always said that you may keep input tax credit only where the tax has actually been paid to the government. For the first five years of GST that was a condition nobody could test. You had no way of knowing whether your supplier had paid, and the department had no mechanism to tell you.
Rule 37A, inserted with effect from 26 December 2022, supplied the mechanism. It converts a principle into two dates.
The two dates
30 September. The supplier must have furnished his GSTR-3B for the period in which he reported your invoice, by 30 September of the financial year following the year in which the credit was availed. GSTR-1 is not enough. GSTR-1 reports the invoice, which is what puts it in your GSTR-2B and lets you claim. GSTR-3B is the return through which the liability is actually discharged. Rule 37A is about the second.
30 November. If the supplier has not filed that GSTR-3B by 30 September, you must reverse the credit by 30 November of the same year, in your own GSTR-3B. Reverse by that date and no interest arises. Reverse later and interest runs under Section 50.
The gap between the two dates is the point. You have two months to notice the default and act on it. In practice you have less, because nobody is going to tell you.
Worked through
Take an invoice dated 10 August 2025, which the supplier reports in his GSTR-1 for August 2025. It appears in your GSTR-2B for August 2025 and you claim the credit in your August 2025 GSTR-3B. The financial year is 2025-26.
The supplier must file his GSTR-3B for August 2025 by 30 September 2026.
If he has not, you must reverse that credit in your GSTR-3B by 30 November 2026, and you do it by adding the amount to your output liability. There is no separate reversal form.
If he later files that return, whenever that is, you take the credit back. The reclaim under Rule 37A is not subject to the Section 16(4) time limit, so a supplier filing three years late still restores your credit. The money is recoverable. What is not recoverable is the interest, if you reversed late.
Why this is harder than it looks
The rule is easy to state and difficult to operate, for one reason: the portal does not tell you which of your suppliers has failed to file his GSTR-3B.
Your GSTR-2B is built from suppliers’ GSTR-1 filings. An invoice appears in 2B because the supplier reported it, not because he paid the tax on it. A supplier who diligently files GSTR-1 every month and never files GSTR-3B produces a perfectly clean 2B and a perfectly reconciled purchase register, while every rupee of that credit is liable to reversal under Rule 37A.
So the exception you are hunting is invisible in the document you normally reconcile against. This is worth stating plainly because it is the single most common misunderstanding: a clean 2B reconciliation is not evidence of Rule 37A compliance. They test different things.
How to actually find the defaulters
The information is available. It is just not delivered to you.
The Search Taxpayer facility on the GST portal exposes a return filing history for any GSTIN, including which GSTR-3B periods have been filed. It is public and it does not require you to be in a transaction with that supplier.
The realistic approach depends on volume.
A few dozen suppliers. Check them manually once a year, in August. That gives you September to chase and October and November to reverse if the chasing fails.
Hundreds of suppliers. Manual checking is not viable. Rank them by credit value and check the top slice that accounts for most of the exposure, which is usually a small fraction of the count. A supplier representing ₹400 of credit is not worth an hour of anyone’s time. One representing ₹4,00,000 is.
Watch for the pattern that predicts default. A supplier who is consistently late on GSTR-1, or who files GSTR-1 but whose invoices arrive in your 2B months after the invoice date, is a supplier under cash flow strain. That is the population most likely to have skipped GSTR-3B, and it is a much smaller list than your full vendor master.
The commercial answer is better than the compliance answer
Rule 37A is genuinely a credit risk sitting inside your payables ledger, and the effective controls are commercial rather than procedural.
Make the tax component conditional. Release the tax portion of a payment only once the invoice is in your GSTR-2B. This is now common enough in Indian B2B contracts to be unremarkable, and it deals with the Section 16(2)(aa) problem at the same time.
Hold a retention on high-value suppliers into the following year. If a supplier accounts for a large share of your credit, retaining a small percentage until his GSTR-3B for the relevant periods is confirmed gives you real recourse. Without it, your only remedy against a defaulting supplier is a civil claim for the tax you were denied, which is worth about as much as the supplier’s solvency.
Say it out loud during onboarding. Suppliers respond to being told that their filing record is checked. Most defaults are drift rather than intent, and drift responds to attention.
The annual return picks this up
The GSTR-9 changes notified by Notification 13/2025-Central Tax added rows dealing specifically with reclaimed credit, with explicit references to Rules 37, 37A, 38, 39, 42 and 43. Reversals and reclaims now have a designated place in the annual return, which means the department can see them, and which means an unreconciled Rule 37A position is more visible than it used to be.
If you have never run a Rule 37A review, the annual return for the current year is where its absence will show.
The summary
The supplier must file his GSTR-3B by 30 September of the following financial year. If he has not, you reverse by 30 November, interest-free. Reclaim whenever he files, with no Section 16(4) limit. Your 2B will not tell you any of this, because 2B is built from GSTR-1 and Rule 37A is about GSTR-3B. Check the return filing history of your largest suppliers in August, chase in September, reverse in November, and put the tax component of payment on a 2B condition so the problem mostly stops arising.
