Need to customize a Purchase Order number? Once an order is created, you can easily make any necessary changes to your PO number.
To add a PO number select the pencil icon to the right of the current PO number and update as needed.

You can change the PO number in any status except Posted Status. If a PO number has to be changed once an order is in Posted Status, you can select Unpost first, and then edit the PO number.
To refresh the PO number within the invoice, click on the 3-dot menu button, and select Regenerate Invoice. You can then download the updated invoice, or even email it directly to your customer.

VIDEO: How to change an order's PO number, reference number & date