How can I show a customers purchase order on my tax invoice? Can't see the option in editing??

I hope all is well, @user15775.

I can give you the simple ways on how to show the Purchase Order (PO) in your tax invoice in QuickBooks Online (QBO).

You'll need to use a custom field and enter the PO number as you create the invoice. Let me guide you on how. 

1. Go to the Gear icon and select Account and Settings.
2. Choose the Sales tab and go to the Sales form content section.
3. Name the custom field as the PO number, then mark the Internal and Public boxes. 
4. Click Save, then Done.

After that, go back to the invoice, then enter the PO number manually. See the sample screenshot below for your reference. 

Once done, I'd recommend running the Transaction List by Customer Report. Then customise it to show the PO number, Invoice, Account, Description, and more.

Additionally, I've attached some articles on how to personalise sales forms like reorder lines, change column widths, add the quantities, rates, and more. 

• Customise invoices, quotes, and sales receipts in QuickBooks

• Create recurring transactions in QuickBooks Online

If you happen to have other questions or concerns with QuickBooks, please post them here. I'm always here to work with you again, @user15775. Stay healthful.