I have down graded to the basic QB. As a sole trader I found the next subscription up a bit expensive. The box where I used to add customer purchase orders is gone. Help

Having you here is a pleasure, @payment-mikeashb.

The purchase order feature is only available for QuickBooks Online Plus and Advanced. 

Since you downgraded to the basic QBO subscription, this result to the missing box for adding a customer purchase order. If you wish to create and send purchase order, you may need to upgrade your account. 

I'll also be sharing some articles that you may use to manage purchase orders in QBO: 

• Create and send purchase orders in QuickBooks Online.
• Add purchase orders to expenses, bills, or cheques in QuickBooks Online.

If you have additional inquiries regarding using QBO to manage purchase orders, please let me know. I'll be glad to offer my assistance. Have a good day!