Penalty on undisclosed income: fixed levy on withholding-tax liability, with exemption for timely disclosure and payment.
A discretionary penalty applies where assessed income includes categories of unexplained or undisclosed receipts imported by reference to existing provisions; it is levied as a percentage of the tax payable under the withholding-tax provision, is additional to that tax, is not imposed if the income was included in the return and the withholding tax paid within the relevant year, and cannot be duplicated by another penalty for the same income. The enacted text omits an explicit cross-application of existing procedural penalty machinery, creating procedural uncertainty.