S. 147: Reassessment- If the reopening is based on information received from the investigation dept, the reasons must show that the AO independently applied his mind to the information and formed his own opinion. If the reopening is done mechanically, it is void. Also, if the reasons refer to any document, a copy should be provided to the assessee. Failure to do so results in breach of natural justice and renders the reopening void.[ S.148 ]