A registered dealer who claims exemption from payment of tax in respect of any goods on the ground that sale of such goods have been made in the course of inter-State trade or commerce, to a registered dealer for the purposes specified under sub-section (6) of section 8 of the Act, shall obtain a declaration in Form I prescribed under the Central Sales Tax (Registration and Turnover) Rules, 1957 duly filled in and signed by the purchasing registered dealer or any person duly authorised by him in writing in this behalf. He shall furnish the portion marked '' to the assessing authority alongwith the Statement in Form E within three months after the end of the period to which the declaration relates and the portion marked '' shall be retained by him.