Permanent Account Number requirement: specified classes must apply to the Assessing Officer using the prescribed application form before registration or activity. Central Government requires specified classes - exporters/importers with importer exporter codes, central excise assessees and invoice issuers under rule 57AE, and service tax assessees - to apply to the Assessing Officer for allotment of a Permanent Account Number. Existing persons must apply within fifteen days of the notification's publication; persons later falling within the classes must apply before commencing the specified export/import activity or before applying for central excise or service tax registration. Applications must be made to the Assessing Officer in the prescribed application form.