Tax determination for fraud: notice and scaled penalty options conclude proceedings if paid within specified periods. Where tax is unpaid, short paid, erroneously refunded or input tax credit wrongly availed by reason of fraud, willful misstatement or suppression, the proper officer shall serve a show cause notice requiring payment of tax, interest and a penalty equal to the tax, issuing notice at least six months before the limitation for order. Voluntary payment before notice with interest plus a fifteen per cent penalty, payment within thirty days of notice with a twenty-five per cent penalty, or payment within thirty days of order with a fifty per cent penalty will conclude proceedings; the officer must issue the determining order within five years from the return due date or erroneous refund date.