...
a percentage (for example, an oncost rate of 10% means that a pay oncost equal to 10% of a payee's gross pay is applicable)
a fixed monetary amount (for example, an oncost rate of $2.50 means a $2.50 oncost is applicable) - this option is available in v11.37 onward.
Each oncost rate belonging to an oncost header must be assigned to a level of the agreement hierarchy and a hierarchy value. This defines what each oncost rate applies to. Where valid, applicable oncost rates exist at different levels of the agreement hierarchy, Rates and Rules applies the rate that is found at the lowest possible level of the hierarchy. For example, if there is an oncost rate defined for the payee who has filled the corresponding job order, that oncost rate will be applied instead of an oncost rate defined at the country or job order level of the agreement hierarchy.
...