Final answer:
A control plan to prevent paying a vendor's invoice twice includes a purchase order matching system, unique invoice numbering, and accounting software that flags duplicates. Vigilant employees and good communication are also crucial.
Step-by-step explanation:
To prevent a vendor's invoice from being paid twice, a strong internal control plan should be in place. This plan might include implementing a purchase order matching system, where the invoice is matched to the corresponding purchase order and proof of delivery before payment is approved. Additionally, assigning unique invoice numbers and setting up the accounting software to flag duplicate entries can also prevent double payments. Should an invoice be submitted in duplicate, these controls would catch the error before payment is processed.
In the given scenario with Noel, the vigilance and prompt communication were key factors in preventing the overpayment. Noel's actions highlight the importance of having attentive employees and an effective communication system as part of the overall control plan. Nonetheless, it's essential to have automated checks in place to minimize reliance on individual detection and action.