Zero-rating is the GST rule
Section 16 of the IGST Act calls an export of services a zero-rated supply. A registered person can supply without paying integrated tax, under a bond or a letter of undertaking, and claim a refund of unutilised input tax credit. The other route, paying the tax and claiming it back, is for the classes the government notifies. This page does not say every exporter may use that second route.
The letter of undertaking is Form GST RFD-11, filed on the GST portal before the export. The portal guide says it is for a registered person who has not been prosecuted for tax evasion of ₹2.5 crore or more. Two witnesses are part of that form. The filing steps are on the GST portal guide linked above.
The bank advice is not the LUT
Rule 96A says that if you export services without paying integrated tax, and the payment is not received in convertible foreign exchange, or in Indian rupees where the Reserve Bank permits it, within one year or within the period FEMA allows, whichever is later, you pay the tax and the interest within 15 days after that. The commissioner can allow more time. The rule is the reason the bank advice matters. It is evidence the money came in the permitted form, inside the period.
A refund statement for accumulated credit on services asks for BRC or FIRC details. Banks also call an inward advice a FIRA. The FEMA regulation on the export declaration does not use either name. That declaration is the EDF page. Keep the three papers apart: the letter of undertaking, the bank advice, and the export declaration.
Send one invoice and the bank advice, and we will say whether the export papers are the ones the GST rule and the bank each ask for.
When the payer is a platform
If the credit comes from a store or a platform rather than from the client, ask the bank whether it will treat that credit as realisation of the export. This page does not treat a wallet balance or a crypto credit as foreign exchange. Nothing retrieved in the IGST section, rule 96A, or the FEMA export regulations says that it is.
A freelancer who invoices from outside India, into India, is a different direction. That GST question is on the consulting-into-India page. This page is the India-to-abroad direction.