You can set a default return fee that is applied to all returns. This flat rate fee, which is not set by default, is configured in the ReturnManager. The value applied here is returned as the default return fee:

double getDefaultReturnFee()
setDefaultReturnFee(double pDefaultReturnFee)

The value entered as the default return fee is applied towards the refund. You can also create a dynamic return fee that is based upon the value of the return. To generate a dynamic return fee value, extend the following:

protected double calculateReturnFee(ReturnRequest pReturnRequest)

Note that only the default return fee will be used by the system unless you have extended the above method.