Short answer: exporting under a letter of undertaking makes accumulated input credit refundable by formula, not by tracing invoices. Claims are lost on foreign exchange receipt evidence, on turnover figures that do not tie to the returns, and on limitation — rarely on entitlement.
What is being claimed
Two routes, depending on how the export was made:
- Under a letter of undertaking — no tax was paid on the export, so the claim is for accumulated input tax credit attributable to the zero-rated supplies. This is the normal route for services.
- On payment of IGST — the tax paid on the export is refunded.
The rest of this note deals with the first.
The formula
The refund is not "all the credit relating to exports". It is computed by a prescribed formula that scales net input tax credit by the ratio of zero-rated turnover to total turnover.
Three consequences:
- A firm with both export and domestic revenue recovers only the export share, regardless of which inputs actually went where.
- The turnover figures must agree with the returns they are drawn from. A claim built on a separate management working that does not reconcile to the filed returns can be rejected on that alone.
- Credit that is not properly availed cannot be refunded. Availability turns on what appears in GSTR-2B, not on holding a purchase invoice — see input tax credit and GSTR-2B.
Where services claims actually fail
Foreign exchange receipt evidence
The single biggest one, and it is structural.
For exported goods, a shipping bill independently corroborates that the goods left the country. For services, there is no equivalent. The bank realisation evidence is doing all of that work — it is the proof that the supply was made to someone outside India and paid for from outside India.
So it has to be traceable invoice by invoice. A lump-sum remittance covering several invoices, or received into an account that cannot be tied back to specific exports, creates exactly the gap the formula cannot bridge.
Turnover mismatches
Zero-rated turnover in the claim not matching the returns; total turnover computed on a different basis; periods overlapping or omitted. All arithmetic, all fatal, all avoidable by building the claim from the returns rather than alongside them.
Limitation
Applications run from a relevant date, and the limit is applied strictly.
For services the relevant date depends on whether payment was received before or after the supply was made — a distinction that is easy to get wrong and that moves the deadline.
Where credit has accumulated over several periods, the oldest periods expire first. They should be filed first, which is the opposite of the instinct to start with the most recent and best-documented period.
The export position itself
If the supply was never an export, no amount of documentation helps. That is a prior question — see the five conditions.
This matters especially for firms that were previously treated as intermediaries and are now zero-rating following the omission of the deeming provision from 30 March 2026. Credit accumulating from that date is claimable on the new footing; earlier periods are not converted by it. See the intermediary trap is gone.