How do I complete the return portion while leaving the replacement sale open?

If you are unable to complete the return of merchandise and sale of its replacement merchandise at the same time, you can use the Split Exchange option from the Actions button on the Customer or Payment page of the exchange order. This option is used to allow corrections to existing exchanges by dividing the exchange into separate documents, one for the customer return and one for the sales order. Once the exchange is split into two separate documents, you can complete them independently. For more detail, please see the Splitting Exchanges topic.