Good day to you, @marina12.

Allow me to guide you on how to achieve this in your QuickBooks Online (QBO) account.

Once you copied a purchase order (PO) to the bill, you can delete the line item of the PO that you don’t want to bill. Let me show you how:

1. Go to the Expenses menu.
2. Locate and open the Purchase Order.
3. Select the Copy to Bill button.
4. Click the Trash (delete) icon on the line item you don’t want to be billed.
5. When prompted, select Remove line.
6. Then click Save and close once done.

You can also check this article for more details about creating a purchase order in QBO: Create purchase orders in QuickBooks Online.

I’ve also added this link that you can use for reference in paying your bills: Enter and pay bills.

In case you have other questions about PO and Bills in QBO, you can always tag me in your reply. It’s always my pleasure to answer them for you and keep you in working order. Keep safe.