Determination of tax evasion requires notice, interest and penalty; offers admission payment remedies and strict limitation periods. Where tax shortfall or wrongful refund or wrongly availed input tax credit results from fraud or wilful misstatement or suppression of facts, the proper officer issues a show cause notice requiring payment of the specified tax with interest and a penalty equal to the tax. A taxpayer may preempt notice by voluntarily paying tax, interest and a reduced penalty and notifying the officer; if so notified, no notice will be issued for that amount, though the officer may issue notice for any shortfall and must issue a determinative order within the Act's limitation period.