Hi there, @Oli in Plymouth UK!

I'll help add a transaction number to your purchase orders in QuickBooks Online.

You don't have to upgrade your subscription or to create a new custom field. Instead, let's turn on the custom transaction number option directly from your purchase order. I'll show you how.

1. Go to the +New button.
2. Under Vendors, select Purchase order.
3. Select the Small Gear icon at the top.
4. Put a checkmark on the Custom transaction numbers feature to turn it on.
5. Click the X button to confirm and save the changes made.

I'm adding this article to read and learn more about using a purchase order: Create and Send Purchase Orders in QuickBooks Online.

You may also read this reference to see where all your purchase orders are and manage them: How to Run Purchase Order Reports?

I've got you covered if you have any other questions about purchase order transactions. Use the Reply option below to leave a comment and I'll get back to you. Take care always!