What is the procedure adopted for making the assessment under section 147 i.e. income escaping assessment?
The Assessing Officer is required to make an assessment or re-assessment as per the following procedures:

Issue of Notice

The Assessing Officer shall serve on the assessee a notice under Section 148 along with a copy of the order passed under clause (d) of Section 148A, requiring him to furnish return of his income or the income of any other person in respect of which he is assessable under this Act during the previous year corresponding to the relevant assessment year. The return shall be furnished within 3 months from the end of the month in which such notice is issued. This period of 3 months can be extended by AO.​

The notice shall be issued in the prescribed form and verified in the prescribed manner and setting forth such other particulars as may be prescribed; and the provisions of Income-tax Act shall, so far as may be, apply accordingly as if such return were a return required to be furnished under section 139.

Circumstances in which notice can be issued

Notice is required to be issued only when information with the Assessing officer suggests that the income chargeable to tax has escaped assessment. Prior approval of specified authority is also required to be obtained befo​re issuing such notice by the Assessing Officer.

However, no such prior approval is required if the Assessing Officer has passed an order under Section 148A(d) with prior approval of the specified authority stating that the income is escaping assessment.