Financial markets have been thrown a fresh curve ball by the decision to write down 16 billion Swiss francs ($17.5 billion) of Credit Suisse bonds, known as Additional Tier 1 or AT1 debt, to zero as part of a forced rescue merger with UBS (UBSG.S).
Under the deal, holders of Credit Suisse AT1 bonds will get nothing, while shareholders, who usually rank below bondholders in terms of who gets paid when a bank or company collapses, will receive $3.23 billion.
Source : Markets in an uproar over AT1 bank bond: a brief explanation