The margin requirement for a short call position can be reduced by holding a long position in the underlying asset.

When the short call is covered by the corresponding long position in the asset (i.e., in the case of a covered call), no additional margin is required. However, it is important to note that the asset used to cover the short call will not be considered as available collateral.

As a result, in case of a covered call, the collateral on the underlying position value will not be offered anymore.