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A small business files GST returns from its books but never checks whether the portal data agrees, and gaps in credit and tax build up unnoticed.
Four matches cover it: sales register to GSTR-1, GSTR-1 to GSTR-3B, purchase register to GSTR-2B, and GSTR-3B to the books.
Monthly download of GSTR-1 and GSTR-2B data, sales and purchase registers from the accounting system, a simple difference sheet per match.
Tax paid and credit claimed that agree with the portal each month, with any gap explained before filing.
GST reconciliation means matching your own sales and purchase records with what the GST portal holds, so that the tax you pay and the credit you claim agree with the returns you filed. Think of it as checking that your books, your returns and the portal all tell the same story every month.
Which records are matched with which?
There are four basic matches. Each compares two sources that should agree.
| Match | Source A | Source B | What a gap usually costs | When in the month |
|---|---|---|---|---|
| 1 | Sales register | GSTR-1 | Wrong data passed to customers; their credit is hit | Before the 11th |
| 2 | GSTR-1 | GSTR-3B Table 3.1 | Tax under-paid, interest, a DRC-01B notice | Before the 20th |
| 3 | Purchase register | GSTR-2B | Credit lost or claimed wrongly | After the 14th |
| 4 | GSTR-3B totals | Books (GST ledgers) | Ledger balances that do not tie at year end | Month end |
GSTR-1 is your sales return, listed invoice by invoice. GSTR-3B is the monthly summary where you declare tax and pay it. GSTR-2B is a statement the portal builds for you on the 14th, showing the purchase invoices your suppliers reported.
Why does it matter?
Because the portal, not your books, decides what credit you can take. Under Section 16(2)(aa) of the CGST Act, 2017, input tax credit is allowed only for invoices that appear in GSTR-2B. And the system compares your GSTR-1 with your GSTR-3B automatically; if the tax in GSTR-3B is lower, a DRC-01B notice can follow. Interest at 18% a year under Section 50 runs on any tax paid late.
Worked example: the ₹18,000 surprise
A small Chennai distributor has a normal month:
- Sales: ₹10,00,000, GST at 18% = ₹1,80,000 output tax
- Purchase register shows ITC of ₹1,08,000
- Planned cash payment: ₹1,80,000 minus ₹1,08,000 = ₹72,000
On the 14th, GSTR-2B shows only ₹90,000 of credit. Two suppliers have not filed yet. The business can claim only ₹90,000 this month, so cash tax is ₹1,80,000 minus ₹90,000 = ₹90,000. That is ₹18,000 more than planned.
Reconciliation is what tells the owner, before the 20th, that the ₹18,000 is a timing gap with two named suppliers, and not a cost. It also tells them whom to call.
Is GST reconciliation the same as GSTR-2B reconciliation?
No. GSTR-2B reconciliation is match 3 only: the purchase side. It gets the most attention because that is where credit is won or lost. But a business that only matches GSTR-2B can still under-report sales in GSTR-3B, or file GSTR-1 data that does not match its books. Those mismatches hurt your customers’ credit and draw notices of their own.
The sales side has its own name in some teams: sales reconciliation, which also ties invoices to bank receipts. See what sales reconciliation is for that wider view.
How do small businesses usually do it?
Most start in Excel: export the sales and purchase registers from Tally or Zoho Books, download GSTR-1 and GSTR-2B data from the portal, and match invoice by invoice on GSTIN, invoice number and amount. A few hundred invoices a month is manageable this way. The key is to do it every month, not at year end.
What to read next
Next, follow a single invoice through the system: how one invoice travels from a supplier’s GSTR-1 to your GSTR-2B and GSTR-3B. Then read the practical purchase-side workflow in GSTR-2B vs purchase register reconciliation, and keep the GST reconciliation glossary open for terms.
GST outward reconciliation (GSTR-1 and GSTR-3B) leads the TransactIG GST roadmap; inward matching (GSTR-2B, ITC, IMS) is on the roadmap. See the GST reconciliation page.