Determination of tax evasion triggers notices and escalating penalties where tax is unpaid, with payment options closing proceedings. Determination of tax not paid, short paid, erroneously refunded or wrongly availed input tax credit by reason of fraud or wilful misstatement or suppression of facts proceeds by service of a show-cause notice specifying tax, interest and a penalty equivalent to tax; statements may extend allegations to other periods where grounds match; voluntary or timely payments at prescribed reduced penalty rates conclude proceedings; the proper officer may issue orders after considering representations and within the statutory limitation tied to annual returns or erroneous refunds.