(22)Credit protection premiums should depend only on the outstanding size and credit risk of the protected tranche. Non-contingent premiums should not be permitted in STS on-balance-sheet securitisations as they could be used to undermine the effective risk transfer from the originator as protection buyer to the protection sellers. Other arrangements, such as upfront premium payments, rebate mechanisms or overly complex premium structures, should also be prohibited for STS on-balance-sheet securitisations.