Determination of tax for fraud or willful suppression triggers notice, interest and escalating penalty remedies. Where a proper officer finds tax not paid, short paid, erroneously refunded or input tax credit wrongly availed by reason of fraud, wilful misstatement or suppression to evade tax, he shall serve a notice requiring the person to show cause why the specified tax, interest under section 50 and a penalty equivalent to the tax should not be paid; the officer may issue related statements deemed to be notices for other periods when non fraud grounds are identical, and the officer must determine tax, interest and penalty and issue an order within the statutory limitation period.