Use and custody of Forms E I/E II govern exemption claims and mandatory submission and retention obligations. Claimants of exemption on subsequent registered sales must obtain correctly completed certificates in Forms 'E-I' and 'E-II', with sellers retaining counterfoils and delivering original and duplicate portions to purchasers. Certificates must be issued by the Commissioner and registered dealers must maintain a register, retain counterfoils for the prescribed period, submit originals with reconciliation returns within prescribed timelines, produce duplicates on request, and furnish quarterly utilization accounts, including nil returns.