Invoice requirements for excisable goods: serialisation, authentication and format govern lawful removal under central excise. The invoice is the mandatory document for clearance and assessment of excisable goods, required to be serially numbered (machine- or computer-generated), include prescribed particulars (registration number, consignee, description, transport, duty details), be prepared in triplicate with specified markings, and have any extra copies marked 'NOT FOR CENVAT PURPOSE.' Controls require one active invoice book unless authorised otherwise, notification of serial numbers for multiple sets, authentication of each invoice leaf by an authorised person, rounding duty to the nearest rupee in figures and words, and specified cancellation procedures; removals for processing or testing require proper documents.