How can i enter a purchase order on an invoice

Thanks for taking the time to post your concern here in the Community, @vividimpressions.

The information from the purchase order cannot be directly added to the customer invoice. With the new QBO structure, you must go to the Custom fields page. This allows you more freedom to include distinct information and insights in your reports in detail. To do this, here's how:

1. Go to Settings ⚙ or the Gear icon.
2. Select Custom fields.
3. Click the Add field button.
4. Enter a name in the Name field (for example, PO Number).
5. Select the All Sales forms checkbox.
6. Turn on the Print on form switch for the custom field to appear on printed and delivered forms.
7. Select Save.

Once you're done, you'll have to manually enter the PO number in the custom field while creating your invoice.

You can read this article for more details: Add custom fields to sales forms and purchase orders in QuickBooks Online.

Also, you might want to use the linked article as a guide to help you customize and include particular information on your sales forms in QBO: Customise invoices, estimates, and sales receipts in QuickBooks Online

As always, you can get back to me if you have any additional questions. I'm here for you. Have a great day!