Printer Billing Logic for Substitute Document Tracking

The system performs preliminary actions by storing correspondence information that links substitute documents to their original target documents before printing occurs. When a substitute document is printed, the system retrieves the pre-stored correspondence information to identify the original document, allowing it to subtract billing units only for the original document rather than charging for the substitute document. This preliminary preparation of correspondence data enables accurate billing differentiation between original and substitute documents.

The correspondence information acts as an intermediary element between the substitute document and the original document. Instead of directly analyzing whether a printed document is original or substitute (which would complicate the billing logic), the system uses the correspondence information as a mediator to link the substitute document to its original counterpart. This intermediary approach allows the system to maintain simple billing subtraction logic while achieving precise document type differentiation through the intermediary correspondence data structure.