Cancellation and storage of documents. Documents taht have been entered into the system should be candeled so they cannot be inadvertently of fraudulently reentered into the system. Paper documents should be defaced, for example, by stamping them "paid." Electronic documents can be similarly "canceled" by setting a lang field to indicate that the document has already been processed. Note: Cancellation does not mean disposal. Original source documents (or their electronic images) should be retained for as long as needed to satisfy legal and regulatory requirements.