Reopening of assessment allows cancellation and fresh assessment when procedural denial or sufficient cause prevented compliance. Where an assessee applies to cancel an assessment on grounds that return filing or response was prevented by sufficient cause, or that notices were not received or opportunity to comply was absent, the income-tax officer, if satisfied, shall cancel the assessment and proceed to make a fresh assessment under the relevant assessment provisions; procedural safeguards required disposal of such applications within a specified period, excluding delays attributable to the assessee.