Topics: Custom software & SaaS, AI automation
Want this done for your business? Get a fixed quote or book a free 30-minute call.
Quick answer: Automate the matching, not the judgement. Pull your purchase register from Tally or your ERP and your GSTR-2B and IMS data from the GST portal, clear exact matches with rules, use AI for near-misses such as reformatted invoice numbers, supplier name variants and split invoices, and auto-draft reminders to suppliers whose invoices are missing. Your accountant still decides ITC eligibility, IMS rejections and blocked credits.
Somewhere between the 11th and the 20th of every month, an accounts team in India opens two lists that should agree and don't. One is the purchase register; the other is what suppliers reported to the GST portal. The gap between them is input tax credit you can't yet claim, which makes reconciliation a cash-flow job rather than paperwork. This guide shows which parts of that monthly cycle software can take over, where AI genuinely helps and where it shouldn't be trusted.
Why does GSTR-2B reconciliation take so long every month?
Because ITC depends on suppliers' filings, and suppliers' data rarely matches your books character for character. Section 16(2)(aa) of the CGST Act allows input tax credit only when the supplier has reported the invoice and it's communicated to you in GSTR-2B. Anything missing or mismatched is credit you can't take this month.
Typical reasons a line won't match:
- The supplier filed GSTR-1 late, or not at all
- The invoice number was keyed differently: "INV/24-25/0123" in theirs, "123" in yours
- The invoice was booked under a branch or a different GSTIN
- Dates differ between the invoice and your booking
- Small rounding differences in tax amounts
- One invoice booked as two entries, or two invoices combined
- Credit and debit notes recorded in a different month
Multiply that by hundreds of suppliers, add several GSTINs, and the work lands on the same few people in the week GSTR-3B is due.
How has the Invoice Management System changed the process?
IMS adds a decision step: you now accept, reject or keep pending each supplier record before it shapes your GSTR-2B. It has applied since the October 2024 tax period, and the GSTN's advisories on the GST portal describe how it works.
The essentials:
| Action | What it does |
|---|---|
| Accept | The record counts towards your ITC in GSTR-2B |
| Reject | The record is excluded, and the supplier's liability is affected |
| Pending | The record is held back from the current GSTR-2B for a later period, with limits on which documents can be held |
| No action | Treated as accepted when GSTR-2B is generated |
The draft GSTR-2B is generated on the 14th of the following month, based on actions taken by then. You can still change actions until you file GSTR-3B, but you must recompute GSTR-2B for the change to count. In practice, reconciliation now has to happen inside a tight window: after suppliers file and before your return. Doing nothing isn't neutral, because unreviewed records are accepted by default.
The practical consequence is that review can't wait for the day before GSTR-3B. If your team only looks at suppliers' data after the 14th, every rejection means recomputing GSTR-2B under deadline pressure. Automation helps most here: records appear on the IMS dashboard as suppliers file, so a match that runs daily surfaces exceptions while there's still time to ask questions.
What can simple rules do, and where does AI matching help?
Rules clear the exact and near-exact matches; AI helps with the messy middle; people decide anything that changes tax. In most businesses, careful rules handle the bulk of lines, leaving AI to suggest matches for what remains.
| Mismatch | Rule-based | AI-assisted | Who confirms |
|---|---|---|---|
| Same GSTIN, invoice number, date and value | Automatic match | Not needed | Nobody, if within tolerance |
| Rounding difference of a rupee or two | Tolerance rule | Not needed | Spot-check |
| Invoice number formats differ | Normalise prefixes, zeros and separators | Suggests matches the rules miss | Accounts team |
| Supplier trade name vs legal name | Match on GSTIN | Maps vendor master variants | Accounts team |
| Date shifted by booking delays | Date-window rule | Ranks likely candidates | Accounts team |
| One invoice split, or two combined | Hard to express as rules | Proposes many-to-one matches | Accountant |
| Wrong GSTIN or branch | Flag only | Suggests the likely entity | Accountant |
Good AI matching shows a confidence score and the reason for each suggestion, learns from the matches your team accepts, and never posts anything by itself. If you already capture purchase invoices with AI document processing for invoices, the cleaner input data makes matching noticeably easier.
How do you connect Tally or your ERP to the reconciliation flow?
Export the purchase register on a schedule, fetch GSTR-2B and IMS data from the portal, and keep both raw files for audit. The automated flow:
- Purchase data. Export the purchase register from TallyPrime or your ERP. Tally can be automated through its XML interface or ODBC; most ERPs offer an API or scheduled export.
- Portal data. Download the GSTR-2B and IMS data from the GST portal, or fetch it through a GST Suvidha Provider (GSP) via API.
- Normalise. Clean GSTINs, invoice numbers, dates and amounts into one format.
- Match. Run rules first, then AI suggestions on the remainder.
- Review. The accounts team works through a short exception list instead of the full register.
- Act. Record IMS decisions on the portal, recompute GSTR-2B if needed, and update the books.
- Archive. Store the raw files, the match results and who approved each exception.
Recent TallyPrime releases include GSTR-2B reconciliation, which may be all a single-GSTIN business needs; check whether your release covers the IMS actions too. For the plumbing between systems, see our guide to Tally integration.
How do you chase suppliers for missing invoices automatically?
Generate one message per supplier listing their missing invoices, send it on WhatsApp or email, and follow up on a schedule. Supplier chasing is one of the most rewarding repetitive tasks to automate with AI, because it's predictable and nobody enjoys doing it.
A workable schedule:
- After the draft GSTR-2B (the 14th): send each supplier a list of invoices you hold that they haven't reported, with numbers, dates, values and your GSTIN.
- A few days before your GSTR-3B is due: send one reminder to suppliers who haven't fixed it.
- The following month: escalate repeat offenders to the purchase manager, who may hold payments under your own commercial terms.
Messages should be polite, specific and easy to act on. AI can draft them in English or Hindi and adjust the tone for long-standing suppliers, but the invoice details must come straight from your data, never from the model's memory. WhatsApp messages from a business system need the WhatsApp Business API and approved message templates.
Which decisions must stay with your accountant?
Anything that changes how much tax you pay or claim. Automation should prepare these decisions with evidence, not make them.
| Decision | Why a person must make it |
|---|---|
| ITC eligibility and blocked credits | Section 17(5) blocks credit on certain goods and services regardless of matching |
| IMS rejections | Rejecting affects the supplier's liability and your relationship |
| Reverse charge | Liability and credit follow different rules |
| Partial matches with tax differences | Someone must decide which figure is right |
| Time limits | Section 16(4) sets a deadline for claiming credit for each financial year |
| Credit note treatment | ITC may need reversing, and timing matters |
A useful habit is a monthly sign-off sheet. The automation lists every exception, the accountant records a decision and a short reason against each, and the sheet is saved with that month's raw files. When a query arrives years later asking why a credit was claimed, the answer and the supplier data behind it are already on file.
Should you buy a GST tool or build a custom workflow?
Start with an established GST tool or your accounting software's reconciliation; build custom when several GSTINs, ERPs or approval steps make packaged tools awkward.
Packaged tools suit businesses with one or two GSTINs, a standard accounting package and a modest number of suppliers. A custom workflow earns its cost when you run several entities on different ERPs, need supplier chasing tied into procurement, or want approval steps and audit trails that match how your finance team actually works. For scale, GRWW typically quotes ₹1.5–5 lakh for a simple custom tool in India, with maintenance of roughly 15–25% of the build cost each year. Our checklist for GST-ready business software helps you assess what you already have.
Frequently asked questions
Can AI do GST reconciliation automatically?
AI can do most of the matching, especially the near-misses that rules miss, and it can draft supplier reminders. It shouldn't decide ITC eligibility, IMS rejections or anything that changes your tax position; those need a qualified person.
What is the Invoice Management System in GST?
It's a GST portal feature that lets you accept, reject or keep pending each supplier invoice before it feeds into GSTR-2B. Records you don't act on are treated as accepted when GSTR-2B is generated.
Does TallyPrime reconcile GSTR-2B?
Recent TallyPrime releases include GSTR-2B reconciliation, showing matched, mismatched and missing invoices. Check your release's documentation for its current IMS support.
How do I chase suppliers who have not filed GSTR-1?
Send each supplier a specific list of the missing invoices, with numbers, dates and values, soon after your draft GSTR-2B is generated, then follow up before your GSTR-3B is due. Automating this with WhatsApp or email templates keeps it consistent every month.
Can I claim ITC if an invoice is missing from GSTR-2B?
Generally no. Section 16(2)(aa) requires the invoice to be communicated in GSTR-2B, so you claim it in a later period once the supplier reports it, within the Section 16(4) time limit. Confirm specific cases with your CA.
Want the monthly match to run itself?
We build custom automation for finance teams that pulls data from Tally or your ERP, matches it against GSTR-2B, drafts supplier reminders and leaves the tax decisions with your accountant. Tell us how many GSTINs and suppliers you handle and we'll send a fixed quote, usually within one business day.