The clearest indicator of direct cost savings is that the organization captured early-payment discounts on eligible invoices. Paying invoices in time to obtain discounts reduces the actual cash paid and generates measurable savings. No duplicate payments and matching invoice amounts are important controls, but they indicate payment accuracy rather than active savings. Paying 95% of invoices by the due date indicates timeliness and avoids penalties, but it does not necessarily show savings. Internal auditors reviewing accounts payable efficiency should evaluate discount capture, duplicate payment prevention, payment timing, vendor terms, invoice accuracy, and exception handling. Since early-pay discounts directly reduce expenditure, Option C is the best indicator that the organization is saving money.