(1)  Notwithstanding anything to the contrary contained in section 73 or section 74, where a registered person fails to furnish the return under section 39 or section 45, even after the service of a notice under section 46, the proper officer may proceed to assess the tax liability of the said person to the best of his judgment taking into account all the relevant material which is available or which he has gathered and issue an assessment order within a period of five years from the date specified under section 44 for furnishing of the annual return for the financial year to which the tax not paid relates.

   (2)  Where the registered person furnishes a valid return within thirty days of the service of the assessment order under sub-section (1), the said assessment order shall be deemed to have been withdrawn but the liability for payment of interest under sub-section (1) of section 50 or for payment of late fee under section 47 shall continue.