If you have mistakenly issued a normal invoice for a supply of goods or services that should have been treated as a supply made under the Special Economic Zone (SEZ) scheme, you can follow these steps to correct the mistake:
1. Issue a credit note to the recipient for the supply. The credit note should indicate that it is issued to correct the mistake in the invoice and should specify the invoice number and date of the incorrect invoice.
2. Issue a new invoice to the recipient for the supply, correctly indicating that it is a supply made under the SEZ scheme and that it is exempt from tax.
3. Ensure that the credit note and the new invoice are accounted for correctly in your accounting records and reflected in your tax returns.