What indicates a substantial change in a Purchase Requisition after it has been released for approval?

The best indication of a substantial change in a Purchase Requisition after it has been released for approval is a change in quantity ordered. Significant alterations in the quantity represent a fundamental adjustment to the requested resources and can affect budget allocations, fulfillment, and inventory management. This change typically necessitates a reevaluation of the overall procurement strategy and budget implications, leading to potential adjustments in approval processes.

While the other options—change in unit price and change in funding source—can also affect a purchase requisition, they might not reflect the same level of impact as a change in quantity. An adjustment in unit price may not require a drastic reconsideration of the request if the overall number of items remains the same, and a change in funding source alters the financial aspect but doesn't directly indicate a need for altered quantities. Therefore, the change in quantity directly highlights a substantial change to the requisition's intent and functional requirements.