Invoice requirements for taxable services: timing, content and exceptions for financial, transport and online services clarified to ensure compliance. Providers of taxable service must issue a serially numbered, signed invoice, bill or challan within thirty days of service completion or payment receipt, stating the provider's name, address and registration number, recipient's name and address, description and value of the service, and service tax payable; sectoral exceptions allow alternative documentary forms and extended issuance periods, and input service distributors must issue serially numbered documents recording provider and recipient details and the amount of credit distributed.