Levy of interest and penalty in search cases: interest accrues and an administrative penalty may attach to undisclosed income when returns are not furnished.
Where a return required by a search notice is not filed, the provision charges interest on tax determined in the search assessment for the period from the day after the notice deadline until assessment completion, and permits an administrative penalty measured by reference to the tax leviable on undisclosed income determined in that assessment. A conditional bar prevents penalty for the block period if the return is filed, tax is paid with evidence, and no appeal is filed against the returned portion; any undisclosed income in excess of declared amounts remains penalizable. Procedural safeguards include a hearing, higher level approval for large penalties, and specified limitation and exclusion rules.