Field help (PFICLCBAS) 

This field is used to define whether this element must be applied to the ex-tax or tax incl amount.
The element is expressed in percentage and specifies whether the taxes must be calculated before (ex-tax) or after (tax incl.) the percentage has been applied.
The element expressed in amount makes the access to this field impossible. This field takes automatically the value None.
The value Action is used to define a new base by applying a program described by an action.
SEEINFO This possibility is only available for invoicing elements in percentage.