Every month the same conversation happens: the books show one input-tax-credit figure, GSTR-2B shows another, and someone has to decide what goes into GSTR-3B before the 20th. Since the GST portal started locking parts of the return, that decision has far less room for adjustment than it used to.
What actually changed
Two things now drive your return.
Outward liability is locked. From the July 2025 tax period, the auto-populated tax on sales in GSTR-3B is non-editable. It flows from GSTR-1, IFF and GSTR-1A. If an invoice value, GSTIN or place of supply is wrong, you can't quietly fix it in 3B — it has to be corrected in GSTR-1A for the same period, before GSTR-3B is filed, or in the next month's GSTR-1.
Credit flows from IMS into GSTR-2B. The Invoice Management System lets you accept, reject or keep each purchase invoice pending. What you accept builds your GSTR-2B, and GSTR-2B decides your eligible credit. Locking the ITC side of GSTR-3B has been announced and reported for 2026, with timelines that have moved more than once, so check the latest advisory on the GST portal before assuming a particular month.
The trap most people miss: if you take no action on an invoice in IMS, the system treats it as accepted once GSTR-2B is generated. A supplier who types ₹10,00,000 instead of ₹10,000 will inflate your credit unless someone looked. Silence is not neutral.
Why the two figures disagree
Nine times out of ten, the gap is one of these — and none of them means your books are wrong:
- Timing. GSTR-2B is generated on the 14th and only picks up what suppliers filed up to the 13th. An invoice booked in March that the supplier filed on the 16th lands in your April 2B. The purchase is right; the month is different.
- Supplier hasn't filed at all. The invoice exists in your books and nowhere on the portal.
- Wrong GSTIN. Your supplier billed a sister concern's GSTIN, or your own other-state registration.
- Credit notes. The supplier has raised one you haven't booked, or you've booked one they haven't raised.
- Reverse charge and imports. These never appear in 2B the way normal purchases do, and inward supplies liable to RCM still have to be entered by you.
Why chasing a perfect invoice-level match is the wrong move
The instinct is to force every line in the books to tie to a line in 2B for the same month. That's a week of work that produces a number you then can't use, because the two documents are measuring different things: your books record when you received the supply, 2B records when the supplier filed.
The useful question isn't "do these two match this month?" It's "of the credit sitting in my books and not in 2B, how much is timing that will correct itself, and how much is a supplier problem I need to chase?" The first group you carry forward and watch. The second group needs a phone call before the due date.
A monthly rhythm that works
- Through the month: check IMS regularly rather than all at once. Accept what matches your purchase register, reject what clearly isn't yours, and keep genuinely disputed invoices pending.
- On the 14th: download GSTR-2B. Recompute it if you took any IMS action after the first generation.
- 14th to 17th: match at supplier level, not invoice level, first. Only open up the suppliers whose totals differ, and sort the gaps into "timing" and "chase the supplier".
- By the 17th: call the suppliers who haven't filed. After the due date, your leverage disappears until their next return.
- Before filing: check what only you can compute — reverse charge, ineligible credit, and reversals. These aren't auto-filled, and a mismatch here is a common trigger for an automated notice.
- File by the 20th — with the number verified, rather than adjusted at the last minute.
Don't lose credit to the clock
Credit for a financial year has an outer limit: broadly, the earlier of the 30th of November following that year or the date you file the annual return. Invoices left pending in IMS "until we sort it out" have a habit of crossing that line. Every quarter, look at what's still pending and decide — accept it, reject it, or get the supplier to amend it.
The short version
Reconciliation has shifted from being a month-end clean-up to being the control itself. The portal will take what IMS and GSTR-2B say. Your job is to make sure they say the right thing before the 14th, not to argue with the number afterwards.
If your credit is stuck, your suppliers are slow, or nobody has opened IMS in six months, that's exactly the sort of thing we take over — see our GST services.
General information, current as of September 2026, not advice for a specific case. GST and income-tax rules change often — check with us before acting on it.