Assessment proceedings, etc., not to be invalid on certain grounds- (1) No assessment, re-assessment, adjudication,

(2) The service of any notice, order or communication shall not be called in question, if the notice, order or communication, as the case may be, has already been acted upon by the person to whom it is issued or where such service has not been called in question at or in the earlier proceedings commenced, continued or finalised pursuant to such notice, order or communication.