If for any reason any tax payable under this Act, has
escaped assessment or has been under assessed or
assessed at a lower rate than the rate at which it is
assessable, the assessing authority may at any time within
four years from the expiry of the year to which the tax
relates, proceed to assess or reassess the tax, as the case
may be, to the best of its judgment after issuing a notice to
the assessee concerned and after making such enquiry as it
considers necessary:
Provided that the tax shall be charged at the rate at which it would have been charged if such tax had not escaped assessment or, as the case may be, had not been under assessed or assessed at a rate lower than the rate at which it was assessable.
Provided that the tax shall be charged at the rate at which it would have been charged if such tax had not escaped assessment or, as the case may be, had not been under assessed or assessed at a rate lower than the rate at which it was assessable.