Definition: Permanent interest-bearing shares
External debt - IMF
These are deferred shares issued by mutual societies, which rank beneath ordinary shares (which are more akin to deposits than equity in mutual societies) and all other liabilities (including subordinated debt) in the event of a dissolution of the society. They provide "permanent" capital. In the United Kingdom these instruments are non-profit-participating by regulatory requirement; rather, predetermined (but not necessarily fixed) interest costs are payable, with the amounts to be paid not linked to the issuer’s profits; interest costs are not to be paid if this would result in the society breaching capital adequacy guidelines and are nonumulative; but more PIBS can be issued in lieu of a cash dividend.
International Monetary Fund (IMF), "External Debt Statistics: Guide for Compilers and Users; Appendix I. Specific Financial Instruments and Transactions: Classifications", Washington D.C., 2003