(3)In the case of an application for revision under this section by the assessee, the application must be made within one year from the date on which the order in question was communicated to him or the date on which he otherwise came to know of it, whichever is earlier:Provided that the Commissioner may, if he is satisfied that the assessee was prevented by sufficient cause from making the application within that period, admit an application made after the expiry of that period.