Spot GST input tax credit mismatches in Tally with AI

If you run a GST-registered business in India, the most expensive bug in your books isn't a wrong amount. It's a missing one.

Specifically: a purchase invoice that exists in your Tally books but never shows up in your supplier's GSTR-1 — and therefore never appears in your GSTR-2B. That mismatch quietly forfeits your input tax credit until you chase the supplier down. Multiply that by a few dozen vendors over a financial year, and you've left lakhs on the table.

This post is about catching those mismatches earlier, with a lot less spreadsheet wrangling.

What the mismatch usually looks like#

There are four flavors of GST mismatch worth catching in Tally:

1. In your books, not in GSTR-2B. Supplier hasn't filed, or filed under a different GSTIN. You've claimed ITC against an invoice that doesn't exist on the government's side.
2. In GSTR-2B, not in your books. Supplier filed an invoice you never received or already returned. Free money — but only if you actually book the credit.
3. Amount mismatch. Both sides have the invoice; the taxable value or tax amount differs. Usually a rounding or rate misclassification.
4. GSTIN typo. Your invoice was filed against a near-miss GSTIN. The classic 15-character data-entry crime.

In a 200-invoice month, finding these by eye is hopeless. In a 2,000-invoice month, it's also expensive enough to hire someone to do nothing else.

The traditional workflow, and where it leaks#

The honest reconciliation flow most teams run today:

1. Download GSTR-2B as a JSON or Excel file from the GST portal.
2. Export the purchase register from Tally.
3. VLOOKUP one against the other on invoice number + GSTIN.
4. Manually triage the diffs — call suppliers, chase missing invoices, adjust ITC claims.

Steps 1–3 are fine; spreadsheets are good at this. Step 4 is where it leaks. The diff list is long, the context for each row lives in three places, and your team's GST consultant only has so many hours.

What an AI layer changes#

A grounded AI workspace on top of Tally doesn't replace your reconciliation — it makes the triage conversational:

• Ask "show me all purchase invoices over ₹50,000 booked this quarter that don't appear in our most recent GSTR-2B" and get a working list, not a 4,000-row spreadsheet.
• Drill into a row: "what other vouchers have we passed for this supplier in the last six months?" — the context comes back without you having to switch screens.
• Generate a draft follow-up email for each missing supplier, with the specific invoice numbers and amounts pre-filled.

The "AI" part is the easy part. The valuable part is that the system is reading your live Tally data, not a stale export — so the answers are good for as long as your books are good.

A short checklist worth running monthly#

If you do nothing else, run this once at the start of every month, ideally on or after the 14th (when GSTR-2B for the previous month is finalized):

• Reconcile purchase register against GSTR-2B at the invoice level.
• Pull the diff into three buckets: missing in 2B, missing in books, amount mismatch.
• For each missing-in-2B invoice over ₹10,000, send a same-day reminder to the supplier.
• For each amount mismatch, decide before month-end whether to amend your claim or absorb the difference.

For a deeper walkthrough of GSTR-2B, the official CBIC GST portal documentation remains the source of truth. But the part that actually wins back your input tax credit is the human follow-up — and that gets meaningfully easier when the diff is small and the context is one prompt away.

The Tally connector that powers this in Koshio is on the downloads page. It pairs with your existing Tally setup in under five minutes.