Credit you cannot see is credit you will lose
Every month a business in India pays GST on what it buys and takes that amount back as input credit against the GST it collects on what it sells. For most companies this credit is the largest single number in the return. It is also the one number the company does not control: since the portal began issuing an auto-drafted statement of credit, called GSTR-2B, a purchase invoice only earns credit once the supplier has filed it against your GSTIN. Your books can be perfect and the credit still missing, because the supplier's return is late, wrong, or filed under someone else's number.
The failure is quiet. No one sends you an invoice for the credit you did not claim. The two ways it surfaces are a notice, months later, asking why your return claimed more than the portal allowed, with interest attached, or a year-end audit that finds credit lapsed because nobody chased a supplier in time. Both are avoidable with the same discipline: compare three things, every month, line by line, and turn every difference into a decision with a name on it.
Three sources, one list of decisions
E1pi reads three things and nothing is typed in by hand. The portal statement for the month, and the one before it, so an invoice that surfaced last month is not reported as missing this month. The return you actually filed, so the comparison is against what you claimed, not what you meant to claim. And your own books, read live from the accounting software: every voucher that touches an input-tax ledger, whether it was entered as a purchase, a journal, a bank payment or an expense claim. A fourth, smaller source is the public filing record of a supplier, consulted only when that supplier's invoice is missing.
The checks, and why each one exists
A total that agrees proves nothing: two errors of the same size in opposite directions cancel out and both survive. So the first rule is that nothing is compared at the total level. Each portal document is matched to one voucher by the supplier's GSTIN and the invoice number, with the usual tolerance for how people type: slashes, spaces, leading zeros, the year written as 2026-27 on one side and 26-27 on the other. If the number fails, the same tax amount on the same GSTIN within a few weeks is accepted and marked as matched on amount, so you can see which kind of match it was. What does not match is sorted into the checks below.
1. Claimed in the books, not on the portal
You booked the invoice, took the credit and filed it. The supplier did not report it. This is the only bucket where the money is genuinely at risk, so it is first. E1pi then asks the public record whether the supplier filed at all that month. The answer changes the conversation: a supplier who filed and left you out has made a mistake you can ask them to fix in their next return; a supplier who has not filed for three months is a credit risk you should stop extending terms to.
the portal's automated comparison of your return against your statement flags the excess, and you reverse the credit with interest from the month you took it. By then the supplier may be out of reach.
2. On the portal and in the books, under the wrong supplier
The invoice number and the amount match exactly, but the GSTIN does not, because the voucher was entered against a different supplier ledger: a logistics agent instead of the courier that issued the bill, a previous year's vendor with a similar name, or, in one case we have seen, a supplier ledger carrying the company's own GSTIN with a zero mistyped as the letter O. Ordinary software shows this as two unexplained exceptions, one on each side. E1pi pairs them and tells you which ledger to move the voucher to.
the credit is still claimable, but your supplier ledgers are wrong, the year-end balance confirmations with those suppliers fail, and the two phantom exceptions distract from the real ones.
3. On the portal, not in this month's books
The portal shows a document you did not enter this month. There are four honest explanations and E1pi tries each before asking you. The invoice was booked in an earlier month and the supplier reported it late; E1pi searches every month of the books for the number and tells you where it sits. It is an import, where the credit comes from customs data rather than a supplier and the Bill of Entry was simply never entered. The portal itself marks the credit as unavailable, for example a seat in a coworking office in another state, so it should never be claimed. Or nobody ever booked it, which usually means a supplier used your GSTIN for a purchase that was not yours, or a bill never reached accounts.
a genuine invoice sits unclaimed until the deadline passes, or a document that was never yours is accepted by default and becomes credit you were not entitled to.
4. Documents you rejected on the portal
Since the Invoice Management System arrived, you can accept, reject or hold each supplier document on the portal, and a rejection removes it from your credit. A rejection should have no voucher behind it; a voucher should have no rejection in front of it. E1pi checks both directions. Rejections with no voucher anywhere in the books are consistent, typically a supplier's debit note you dispute. A rejected document that is also booked is a contradiction someone needs to look at.
a rejection by mistake forfeits the credit silently, and nothing in the books ever reports it, because the books still show the invoice as claimed.
5. Old invoices surfacing late, and the parking discipline
A careful accounts team books credit for an invoice that is not yet on the portal into an "unclaimed" ledger, and moves it to the claimable ledger with a small journal the month it appears. That is the right discipline, and it must be recognised rather than reported. E1pi reads those transfer journals, ties each to the invoice that surfaced, and lists the pair as explained. It also notes the deadline: credit on an invoice from a previous financial year lapses on 30 November, whatever the reason it was late.
either the invoice is claimed twice, once when booked and once when it surfaces, or it is parked and forgotten past the date after which it cannot be claimed at all.
6. Reverse charge and imports, kept apart
Transport bills under reverse charge do not follow the supplier flow: you pay the tax yourself and take it back. Import credit comes from customs filings, not from a supplier's return. Forcing either into the invoice match produces a page of false exceptions. E1pi reconciles them in their own lanes, against the reverse-charge and import tables of the return.
real exceptions are buried in noise, and the reverse-charge liability that must be paid in cash is the one line nobody looks at.
7. Supplier behaviour, not just supplier invoices
Each supplier gets a line: how many documents they reported, how many are clean, how many are open, the date they filed, whether that was after the cut-off, and how many of their documents belonged to older months. Over a few months this becomes a scorecard. The supplier who is always a month late, the one who reports only after being chased, and the one who has stopped filing are three different problems with three different answers.
the same supplier costs you the same credit every quarter, and the decision to change terms or change supplier is never made because nobody can see the pattern.
8. Masters that block the match
A supplier ledger with no GSTIN cannot be matched automatically; its invoices can only be found by name and amount. A GSTIN with a typo matches nothing. E1pi lists both, because the fix is five minutes and it makes every future month cleaner.
a growing tail of "unmatched" lines that are really the same handful of ledgers, month after month.
9. The return itself
Finally, the three totals side by side, by tax head: what the books claim, what the portal allows, what the return took. They will not be equal, and they should not be. But every rupee of difference must be nameable: this import not booked, those old-period documents deliberately left out, that supplier not yet reported. If the difference cannot be explained line by line, the return is wrong somewhere.
a difference that is simply carried, month after month, until a notice asks for the explanation you no longer have.
10. Memory between months
Every finding is written to an append-only log with a stable key: company, period, bucket, supplier, document. Run the same month again after the supplier amends their return and the item is reported as resolved, not rediscovered. Run next month and the suppliers who were late last time are already known. Nothing is overwritten, which is also what an auditor wants to see.
the reconciliation is a spreadsheet someone rebuilds from scratch every month, and the history of what was found and what was done lives in one person's inbox.
The same ten, in one table
| Check | Why it exists | If it is missing |
|---|---|---|
| Invoice-level match | Totals hide offsetting errors | Two mistakes cancel out and both survive |
| Claimed, not reported | The only credit truly at risk | Reversal with interest after a notice |
| Wrong supplier ledger | Same invoice, different GSTIN | Wrong ledgers, failed confirmations, phantom exceptions |
| Portal only | Late, import, ineligible, or never yours | Credit lapses, or credit you were not entitled to |
| Rejected on the portal | A rejection forfeits credit | A mistaken rejection is never noticed |
| Late invoices, parked credit | Recognise the housekeeping | Double claim, or forgotten past 30 November |
| Reverse charge, imports | Different flow, different table | Noise, and a cash liability unwatched |
| Supplier scorecard | Behaviour repeats | The same supplier, the same loss, every quarter |
| Supplier masters | No GSTIN, no match | A permanent tail of unmatched lines |
| Return versus portal versus books | Every rupee of difference named | A gap carried until someone asks |
A person still holds the pen
None of this sends anything. E1pi does not message a supplier, does not post a correction to the books, does not file. It produces a short list, ranked by money, where each line says what was found and what the next step is. When you decide a supplier should be asked to amend, the message is drafted for you, one per supplier, with the invoice numbers and amounts filled in, and you press send. When a voucher should move to another ledger, that is a correction you approve. The judgement stays with the accountant; the reading, matching and remembering is what the machine takes away.
The portal decides what you may claim. Your suppliers decide what the portal shows. The only part you control is how early you find out.