To add a fee to invoices for a group of parents you would go to Billing tab > Overview. Then click on the top drop down menu and select Add Fee To Invoice. From here, you will select which class(es) and if you wish you can select the specific schedules as well. Click Preview once you are done. This will pull up any child that is currently enrolled in that class/schedule. Select all by clicking the white checkbox on the blue bar and click Add Fee. Then select the fee type (which pulls from Settings > Fee Types), description (optional) and the amount (if different from the default). Click Add Fee when are you done entering in this information. This will then add the fee onto the most recent invoice created.
If you wish to add a fee to one parent’s invoice, you would click the down arrow in the parent’s account > Click on the invoice you wish to add the fee to (most likely the most recent one) > Click Add Item. Select which fee you wish to add, comment (optional) and the amount (if different from the default). Click Save at the bottom when you are done.