Why did I receive multiple Confirm Receipt notifications for the same purchase order schedule?

Let's look at an example for why you might receive multiple Confirm Receipt notifications for the same purchase order schedule.

If you run the Confirm Receipts process on 8-Dec-2020, the process checks all purchase orders that have a due date as 7-Dec-2020 or less (with receipt routing as Direct Delivery, match option as 3 Way, a requester present on the purchase order, and destination type as Expense). Then, the process checks if there is an existing notification assigned. If the notification is already assigned, a duplicate isn't sent. When a notification is sent, it's up to the requester to act on it manually. The requester must go to the work list and receive using buttons or the email actions, such as Fully Received or Did Not Receive. If the notification is sent on 8-Dec-2020 and the original requester doesn't respond by 16-December-2020, then another reminder email is sent. If the requester doesn't respond by 23-December-2020, the current notification expires and it's escalated to the original requester's manager.

Also, it's possible to receive a notification two days in a row if an open notification is closed with actions pending, but not done. For example, if the requester selects the Did Not Receive option and closes the notification. In this case, the application sends the notification again during the next run of the Confirm Receipts process.