Section 143(3)

If a case is selected for scrutiny, then it is necessary for assessing officer to complete the assessment proceedings and pass an assessment order u/s.143(3) of the act within time limit as specified under the Income tax Act. If no order is passed, then it is  belived that the order is deemed to be passed. and assessment proceedings is deemed to be closed for that year. 

@ siddharth - For making assessment u/s 143(3) notice u/s 143(2) is to be issued. you have mentioned it as 142(2)