Options and warrants on interest rates, debt instruments, equities, equity indices, financial futures, swaps and foreign currencies shall be treated as if they were positions equal in value to the amount of the underlying instrument to which the option refers, multiplied by its delta for the purposes of this Chapter. The latter positions may be netted off against any offsetting positions in the identical underlying securities or derivatives. The delta used shall be that of the exchange concerned. For OTC-options, or where delta is not available from the exchange concerned, the institution
may calculate delta itself using an appropriate model, subject to permission by the competent authorities
. Permission shall be granted if the model appropriately estimates the rate of change of the option's or warrant's value with respect to small changes in the market price of the underlying.