Banks which have the intention and capability to use internal models for the measurement of their commodities risks and, hence, for the calculation of the capital requirement, should seek the prior written approval of the CBB for those models. The CBB's detailed rules for the recognition and use of internal models are included in chapter CA-14. It is essential that the internal models methodology captures the directional risk, forward gap and interest rate risks, and the basis risk which are defined in Paragraph CA-12.1.4. It is also particularly important that models take proper account of market characteristics, notably the delivery dates and the scope provided to traders to close out positions.