The asset may be constructed on behalf of an ultimate customer or off-taker with whom the Islamic bank licensee enters into a parallel Istisna contract. In this case, there is a credit risk exposure to the ultimate customer for the payment due under the parallel contract. This credit risk occurs upon commencement of the construction work by construction firm, until the whole amount or all the instalments (progress billings) are paid by the ultimate customer. The RW for this credit exposure is that of the ultimate customer, unless there is a guarantee, in which case the RW is that of the guarantor if lower.