Commonwealth Consolidated Acts(1) The unpaid amount of a liability to pay amounts is:
(a) if the liability remains undischarged to the extent of a particular amount--that amount; or
(b) otherwise--a nil amount.
(2) The unpaid amount of an estimate is:
(a) if the liability to pay the estimate remains undischarged to the extent of a particular amount--that amount; or
(b) otherwise--a nil amount.