Determination of tax liability for fraud triggers notice, interest and escalating penalties unless taxpayer pays promptly. Where tax was not paid, short paid, erroneously refunded or input tax credit wrongly availed by reason of fraud or wilful mis statement or suppression, the proper officer shall serve a show cause notice requiring payment of the specified tax with interest under section 50 and a penalty equivalent to the tax. Notices must be issued at least six months prior to the limitation for orders; statements for additional periods may be treated as notices if grounds (other than fraud) match earlier notices. The officer shall determine tax, interest and penalty and issue an order within the five year limitation.