(b) has, in consequence of any information in his possession, reason to believe, notwithstanding that there has been no such omission or failure as is referred to in clause (a), that the net wealth chargeable to tax has escaped assessment for any year, whether by reason of under- assessment or assessment at too low a rate or otherwise; he may, in cases falling under clause (a) at any time within eight years and in cases falling under clause (b) at any time within four years of the end of that assessment year, 1[ serve on such person] a notice containing all or any of the requirements which may be included in a notice under sub- section (2) of section 14, and may proceed to assess or re- assess such net wealth, and the provisions of this Act shall, so far as may be, apply as if the notice had issued under that sub- section.