Penalty for specified unexplained income applies unless the income was disclosed and special tax paid before year-end. An assessing or appellate officer may direct an additional penalty where assessed income includes amounts characterised as unexplained under specified taxable-income provisions, calculated as a percentage of the special tax chargeable on such income and payable in addition to that tax. No penalty applies where the assessee has disclosed the income in the return and paid the special tax by the end of the relevant previous year; general penalty provisions do not apply to such income and specified procedural provisions govern levy and recovery.