Income escaping assessment: notice under Section 148 triggers requirement to furnish a return and may need prior approval. Assessment under Section 147 is initiated by serving a notice under Section 148 when information suggests income has escaped assessment, requiring the assessee to furnish a return treated like a section 139 return; the notice must be in the prescribed form and verified, the filing period may be extended, and prior approval of the specified authority is ordinarily required before issuing the notice unless an order under Section 148A(d) with prior approval has already been passed.