Irredeemable debt – for example, this term refers to a debt towards the Government or towards the Municipality and which can not be liquidated with expiration of any deadlines; it is always due. The Contracts and Obligations Law in many States regulates that the obligations towards the Government are privileged to be paid, before any other debts.

See also http://www.ehow.com/about_6569398_irredeemable-debt_.html