GSTR-2B vs your purchase register: the 7 root causes of mismatch

Every CA firm has a story about GSTR-2B reconciliation. The numbers are within rounding. Or off by tens of thousands. Or off by lakhs. The client is on the phone. The article is in tears. The partner sighs and pulls up a spreadsheet.

Twenty years in, we've seen the mismatch root-cause itself every time. There are seven. Walk down the list in order; one of them is the answer.

Cause 1 — Vendor hasn't filed yet

Most common, least interesting. Vendor's GSTR-1 for the period is not yet filed (or filed late). The invoice is on your purchase register but not on 2B. ITC is not claimable until they file.

Fix:Email the vendor. If they're on a quarterly filing scheme (QRMP), the invoice may not appear until the quarter ends. Move the ITC claim to the next period and tag the invoice as “ITC pending vendor filing.”

Cause 2 — Vendor filed with wrong details

Vendor filed GSTR-1, but typed your GSTIN incorrectly, used the wrong invoice number, or recorded a different invoice date. 2B shows their version. Your purchase register shows yours.

Fix:Identify the affected invoices. Email the vendor to revise GSTR-1 (they can amend in the subsequent month). Until amendment, hold the ITC. Tag in your books as “ITC pending amendment.”

Cause 3 — You booked it in a different month

Vendor filed correctly in May. You received the goods/services and booked the invoice in June. 2B for May shows the invoice; your purchase register for May doesn't. Legitimate timing difference.

Fix:Confirm the invoice IS in your purchase register, just in a later month. The cumulative ITC will reconcile across periods. For monthly 3B prep, mark such invoices as “available on 2B, booked next month” and claim the ITC in the month you booked.

Cause 4 — You booked it but it's not in 2B at all

The vendor may have filed against the wrong GSTIN entirely (i.e., not yours). Or invoiced under a related entity's GSTIN. Or forgotten to invoice at all.

Fix:Pull the vendor's GSTR-1 from GSTN portal. Search by your GSTIN. If the invoice is missing entirely (not on any of your GSTINs), the vendor hasn't reported it. Until they do, you cannot claim ITC. This is the single biggest ITC leakage in Indian businesses.

Cause 5 — Reverse charge confusion

RCM invoices are tricky. The vendor doesn't charge GST on the invoice. They don't report it in their GSTR-1 (because they didn't collect tax). You pay the GST yourself under reverse charge in cash, then claim ITC in the same month.

Your purchase register shows the invoice with GST. Your 2B doesn't. There's no mismatch — the vendor was correct not to file. The ITC comes from your RCM payment, not from 2B.

Fix: Tag RCM invoices clearly in your purchase register. Reconcile them separately against your RCM cash payments, not against 2B. (In TatvaBooks, RCM is a checkbox on the voucher itself, so these never get mixed into the 2B comparison by accident.)

Cause 6 — Credit notes

Vendor issued a credit note in May (reducing the invoice value). Their GSTR-1 reflects the net amount. Your purchase register may still show the gross invoice if the credit note was booked separately.

Fix: Net the credit note against the original invoice in your purchase register reconciliation. If the credit note was issued in a later month, the 2B and register will mismatch in both months but reconcile cumulatively.

Cause 7 — Block-listed vendors and Rule 86A

Rule 86A allows GST authorities to block ITC against specific vendors flagged for fraud risk. The invoice appears in 2B with a blocked tag. You see a number, but you can't claim it.

Fix: Identify Rule 86A blocked invoices. Hold the ITC claim. Investigate vendor status. If genuine, file an application for de-blocking with supporting documents (purchase order, GRN, payment proof). If suspect, stop dealing with the vendor.

The systematic reconciliation order

When you sit down to reconcile a difficult month, walk the list in this order. It eliminates the largest buckets first.

1. Generate the 2B from GSTN for the period.
2. Total it. Compare to your purchase register total. Note the gap.
3. Filter your register for RCM invoices. Subtract. (Cause 5)
4. Filter for invoices booked in the period from prior-month vendors (timing differences). Set aside. (Cause 3)
5. Net out credit notes. (Cause 6)
6. What's left is the real mismatch.Now investigate item by item — Cause 1 (vendor hasn't filed), Cause 2 (vendor filed wrong), Cause 4 (not in 2B at all), Cause 7 (Rule 86A blocked).

In a clean month, steps 3-5 explain 80% of the gap. In a difficult month, step 6 takes the most time but is mechanical — line by line.

Prevention beats reconciliation

The best reconciliation is the one you don't do. Three habits that reduce 2B mismatches at the source:

• Vendor onboarding includes a GSTIN verification.Pull their filing history before the first invoice. Avoid vendors who file late or miss filings.
• RCM invoices get a dedicated tag in your accounting system. Never reconcile them against 2B by accident.
• Period-end check before locking the month. Spot the missing 2B entries while the vendor relationship is fresh, not three months later when nobody remembers.

And if your accounting product can take the GSTR-2B you import and surface the mismatches with these seven buckets pre-classified — that's an hour saved on every reconciliation cycle, every client, every month. We built ours that way for our own articles. The product happens to be on the market now.

Reconciling ITC is one half of the monthly cycle; closing the outward side is the other. If you file GSTR-1 too, our checklist for closing GSTR-1 in 60 minutes runs the same prevention-first discipline. And keep the GSTR-3B due date in view — the period you claim corrected ITC in is the period it has to land.

— Anil