Fraud based tax determination triggers show cause notices and prescribed penalties with opportunities for curtailed proceedings on timely payment. Where non-payment, short payment, erroneous refund or wrongful availing/utilisation of input tax credit arises from fraud, wilful misstatement or suppression, the proper officer may serve a show-cause notice requiring payment of the specified tax with interest and a penalty equal to the tax; a taxpayer may avert notice by earlier payment with interest and a reduced penalty, and payments within specified short periods after notice or order conclude proceedings, while the officer must determine amounts by order within the statutory limitation period.