An invoice is not a necessary requirement for a creditor claim the status of an operational creditor. A demand notice can be issued based on other documents evidencing a contract for supply of goods or services can prove that an entity is an operational creditor.
In CCCL v Hitro Energy Solutions Pvt Ltd 2022 INSC 150 where the Supreme Court noted that an invoice is not sine qua non to successfully claim the status of an operational creditor. A demand notice based on other documents is sufficient is the creditor received goods/services from corporate debtor.