Change of opinion doctrine limits reassessment and requires tangible material and a live link to justify reopening. Change of opinion presupposes a previously formulated view and precludes reopening based solely on overturning that view; non speaking or cryptic assessment orders may not evidence any prior opinion. Reassessment differs from review and requires tangible material indicating escapement of income and reasons that have a live link to the formation of belief, with the change of opinion doctrine serving as a check against abuse.