This error message appears if you attempt to add a new price (potential billing charge) to the billing charges list by clicking on the New Price button beneath that list without first selecting a price sheet and category that the new billing charge will belong to in that list (by clicking on the category). Click OK to clear the error message. Then, select the appropriate category in the potential billing charges list before clicking on the New Price button again. If the appropriate price sheet and/or category does not exist in the list, see Creating a New Price Sheet for instructions on how to create this.