For instruments that deviate from the above structures, or could be considered complex, each bank should agree a written policy statement with the Central Bank about the intended treatment, on a case-by-case basis. In some circumstances, the treatment of an instrument may be uncertain, for example bonds whose coupon payments are linked to equity indices. The position risk of such instruments should be broken down into its components and allocated appropriately between the equity, interest rate and foreign exchange risk categories. Advice must be sought from the Central Bank in cases of doubt, particularly when a bank is trading an instrument for the first time.