Determination of tax not paid: show-cause notice requires payment with interest and may attract penalty if not remedied. Determination of tax not paid, short paid, erroneously refunded or input tax credit wrongly availed or utilised (except where fraud or wilful misstatement or suppression of facts is involved) is initiated by the proper officer by issuing a show-cause notice requiring payment of the specified tax with interest under section 50 and a penalty. A detailed statement for additional periods may be deemed a notice if based on the same grounds. Voluntary payment of tax with interest before notice bars subsequent notice for that amount, although inadequate payments may be further pursued.