Reopening an assessment beyond the four year period is...

Reopening an assessment beyond the four year period is impermissible unless the assessee failed to fully and truly disclose material facts; here the taxpayer had disclosed investments, dividend receipts and redemptions, so the proviso to the reopening power was not satisfied and the reassessment represents a change of opinion. The reopening notice contained general, inconsistent allegations about dividend stripping without specific material showing the assessee's knowing participation. The AO's recorded reason (fictitious short term loss) differs from the final treatment (treating dividend as unexplained credit), so reassessment cannot be sustained; accepted transactions preclude treating dividend as unexplained cash credit.