Glad to have you back, @Michael Hunter.

I can help you customise your invoice template and have the PO number to show up. This can be done by adding a custom field. Let's do this.

You have the option to add a custom field on any of your sales forms to add your desired information on your transaction in our Plus package

To do that:

1. Click on the Gear icon at the top.
2. Select on Custom Form Styles.
3. Click on the New Style button.
4. Choose Invoice.
5. Select the Content tab.
6. Tick on the upper part of the sample invoice in the right.
7. Refer to the Display section.
8. Tap on the Custom Fields button.
9. Put a check-mark on the box and enter the PO number.
10. Click on Save. 

From then on, you can now enter PO numbers on your invoice transaction.

That should do the trick, Michael.

I've included here some resources that you can check out about customising and handling sales forms in QuickBooks Online for your future reference:

• Customise your invoices, estimates, and sales receipts in QuickBooks Online
• How to customise an invoice

Please let me know how these setups work for you. I want to ensure you'll get what you need. Take care!