Invoice requirements: goods triplicate and services duplicate, with mandated electronic reporting and notified e invoicing and exemptions. Rule 48 mandates invoice formats: triplicate copies for goods and duplicate copies for services, and requires furnishing invoice serial numbers electronically via the common portal. Certain notified classes must upload prescribed invoice particulars and obtain an Invoice Reference Number on the portal; the Commissioner may exempt classes from this requirement. Invoices issued otherwise than in the prescribed electronic manner are not treated as invoices, and the conventional copy format rules do not apply to electronically issued invoices.