If, in consequence of definite information which has come into his possession, the Income- tax Officer discovers that profits of any chargeable accounting period chargeable to business profits tax have escaped assessment, or have been underassessed, or have been the subject of excessive relief, he may at any time within four years of the end of the chargeable accounting period in question serve on the person liable to such tax a notice containing all or any of the requirements which may be included in a notice under section 11, and may proceed to assess or reassess the amount of such profits liable to business profits tax, and the provisions f this Act shall, so far as may be, apply as if the notice were a notice issued under that section.
