Receipts on or before the promised date divided by receipts, per supplier, per month. With quality from rejections, the performance trend that warns before a supplier fails.
Receipts without one cannot be measured. Count them and get the date onto the purchase order.
A supplier at 91 percent is fine; a supplier that was at 96 and is now at 91 is the finding, especially if it is the single source for fourteen parts.
Receipts or deliveries inside the agreed date window divided by those due, per supplier or customer, per month, with the window stated.
Seven of ten lines arrived within one day of the requested date: 70 percent. Against the promised date, which had been moved twice, it was 100 percent.
Measured against a promise that was changed after the order. Everything is on time to a date nobody wanted.