5 GST Reconciliation Errors That Cost CAs Their Clients

Every month, thousands of CA firms across India reconcile GSTR-2B against their clients' purchase registers. Most do it in Excel. Most miss at least one of these five errors — not because they are careless, but because Excel was not built to catch them.

1. Tax Type Mismatch (CGST/SGST vs IGST)

This is the most underappreciated error in GST reconciliation. A supplier registers as an intra-state vendor in your books, but files the invoice as inter-state (IGST) in their GSTR-1. The invoice appears in your 2B as IGST. Your books show CGST/SGST. A standard VLOOKUP on invoice number will show a match — because it does not compare the tax type.

The result: you have claimed the wrong tax component. During a scrutiny assessment, this is a straightforward ITC disallowance.

2. Cross-Month Invoices Marked as Missing

Suppliers are supposed to file GSTR-1 by the 11th of the following month. Many do not. An invoice dated March 2025 may appear in your 2B only in May or June. If your reconciliation only matches the current month, that invoice shows as "missing from 2B" — and you may advise the client to reverse ITC that is actually recoverable.

The correct approach is to match across a rolling 3-month window before marking an invoice as genuinely missing.

3. Duplicate Entries in the Purchase Register

A single supplier sends an invoice. Your accounts team books it twice — once when the invoice arrives, once when the payment is made, or once in each branch office's books. Both entries appear in your reconciliation input. The tool matches both to the same 2B entry.

The net result: you have booked and potentially claimed ITC twice for one invoice. When the department reconciles your GSTR-3B against GSTR-2B, the excess claim stands out.

4. Amount Tolerance Errors

Your purchase register shows ₹1,00,000 as the taxable value. The supplier reported ₹1,00,001 in GSTR-1 — perhaps a rounding difference, perhaps a minor correction. A strict exact-match reconciliation marks this as a mismatch. An experienced CA knows it is immaterial. A junior doing the reconciliation may raise it with the client, wasting everyone's time.

The opposite is also true: a ₹5,000 difference on a ₹1,00,000 invoice is material and should be investigated. A good reconciliation tool lets you set a tolerance threshold — amounts within the threshold are treated as matched, amounts outside are flagged.

5. Missing-from-Books Invoices (Missed ITC)

Your supplier filed the invoice in GSTR-1. It appears in your 2B. It does not appear in your purchase register. This means you have not booked the expense, you have not claimed the ITC, and depending on the amount, your P&L may be understated.

This is the error most reconciliation processes never catch — because most processes only check what is in your books against 2B, not what is in 2B that is absent from your books. In a manual Excel process, checking the reverse direction requires an additional, separate VLOOKUP pass that is easily skipped.

All five of these errors are caught automatically by ReconBridge. If you are currently reconciling in Excel, the question is not whether you are missing some of them — it is how many you are missing per client per month.