Tax invoice requirements: specialized contents and electronic issuance rules govern ISDs, consolidated invoices, transport and ticketed services. Rule 54 mandates special invoice and document contents for Input Service Distributors, credit transfers by registered persons sharing PAN and State code, consolidated monthly invoices for insurers and financial institutions, detailed invoices for goods transport agencies, and tickets or electronic tickets as tax invoices for passenger transport and multiplex film admissions; signature requirements are relaxed for electronic documents under the Information Technology Act and these provisions apply mutatis mutandis to related rules.