The CalculateRateForNullMarkup property controls how the system will handle markups on orders where no markup has been predefined. This includes the possibility of automatic entry of a markup in empty (NULL) markup fields.
Config Option > Supplier > EmployerSetting
True: OT/DT pay and bill rates get calculated automatically with the standard 1.5/2x markups for New Order provided that the selected customer does not have a custom markup defined in customer's order option.
False: User has to enter rates manually. Rates will not automatically be populated in for unentered rates on new orders.
Where the setting is reflected...
In Customer > Order Options > Markup, or any place a markup is used in order processing.