**Total** – Calculates the total for a return order form.
**SubTotal** – Calculates the total of all shipments in a return order form.
**HandlingTotal** – Calculates the handling total for a return order form.
**ShippingSubtotal** – Calculates the shipping subtotal for a return order form.
**OrderDiscountTotal** – Calculates a return order form discount amount. It is the total of order-level discounts of all line items in all shipments in a return order form.
**DiscountTotal** – Calculates a return order form discount total. It is the total of order-level discount amount and line item discount amount of all line items in all shipments and shipment discount amount of all shipments in a return order form.
**TaxTotal** – Calculates the tax total for a return order form.

## Change the default calculation
By inheriting from the default implementation of the interface, DefaultReturnOrderFormCalculator, you can override the calculations. Just override one or several of the methods in DefaultReturnOrderFormCalculator.
## Change the default validation
The default implementation validates that the totals are not negative after the calculation. To change the behavior, override the ValidateTotal, ValidateSubtotal, ValidateHandlingTotal, ValidateShippingSubTotal, or ValidateTaxTotal method, depending on which validation you should override.