20[Notice deemed to be valid in certain
circumstances.
292BB. Where an assessee has appeared in any
proceeding or co-operated in any inquiry relating to an assessment or reassessment,
it shall be deemed that any notice under any provision of this Act, which is required
to be served upon him, has been duly served upon him in time in accordance with
the provisions of this Act and such assessee shall be precluded from taking any
objection in any proceeding or inquiry under this Act that the notice was—
(a) not served upon him; or
(b) not served upon him in time; or
(c) served upon him in an improper manner:
Provided that nothing contained in this section shall apply where the assessee
has raised such objection before the completion of such assessment or reassessment.]