Tax determination for fraudulent evasion: show cause notice, interest and penalty with specified timelines for assessment closure. The proper officer may serve a show cause notice where tax is not paid, short paid, erroneously refunded or input tax credit wrongly availed or utilised by reason of fraud or wilful misstatement or suppression, requiring payment of the specified tax with interest and a penalty equivalent to the tax; voluntary payment before notice attracts interest and a reduced penalty, payment within thirty days of notice or of the order at higher prescribed penalty rates concludes proceedings, and the officer must issue the assessment order within five years from the due date for the annual return or from the date of erroneous refund.