Input Service Distributor: distribution of credit requires prescribed invoice, limited to available credit and attributed suppliers, allocated proportionately. Distribution of credit by an Input Service Distributor must be effected through a prescribed tax invoice or document, must not exceed the available credit, must be given only to suppliers to whom the services are attributable, and where services are attributable to multiple suppliers the credit must be allocated proportionately based on each supplier's turnover in the preceding financial year.