You can delete a purchase order if you don't need it, GeriR.

The option to delete them one time isn't available in QuickBooks. You'll need to do it one at a time. To do it, open the purchase order, and then click More. Then, select Delete. However, you can look for a third-party app that helps you delete years of transactions one time.

While this option isn't available yet, I'll personally send feedback to our Product Development team to review and determine features to be added in our feature updates.

On the other hand, you can browse the list of common questions about purchase order in this article: Create purchase orders in QuickBooks Online.

Drop me a line if you still need my help.