A clause in a facility agreement (or certain other debt documentation) that allows the lenders, in certain circumstances, to calculate interest on a different basis to that on which it is normally calculated. Usually, the clause is drafted so that it operates if a given percentage of lenders' cost of funds relating to their participation a loan would exceed the otherwise applicable interest rate (excluding the margin). Sometimes, these sorts of clauses deal with unavailability of the applicable interest rate if it is determined by reference to a published screen rate but more frequently unavailability of a screen rate is dealt with separately (for example, via an automatic fallback to a central bank rate).