Items that have been sold to one customer, may wind up in the hands of another customer, such as if the product has been on sold. 

If a Customer Item has been created for an item, it can be reassigned to another customer. Reassigning the Customer Item updates the customer recorded on the Customer Item to the new customer.

To reassign an existing Customer Item

Open the Customers Module, and navigate to the Items function. Locate the Customer Item to be reassigned and open the Spill menu at the end of the line. Choose Reassign to open the reassign dialogue box:

Using the Reassign to dropdown to select the customer to reassign the Customer Item to. Once selected, choose Reassign to complete the reassignment.