I have for only 1 vendor bills open while they have been paid

Hi there, @AP TimH.

Thanks for posting your concern here in the Community space. I can help check why your bill unmarked as paid and even show in the Unpaid Bills Detail report.

The PAID stamp will not appear on the bill if the payment was not recorded through Pay Bills. Paying bills is part of your usual A/P workflow in QuickBooks Desktop.

In case you haven't perform it, follow the detailed steps below:

1. Go to the Vendors menu.
2. Select Pay Bills.
3. Choose the bills you want to pay from the table.
4. Select the payment date and method.
5. Click Pay Selected Bills.
6. When Payment Summary window appears, click Done.

For more information, please refer to the following article: https://quickbooks.intuit.com/community/Income-and-expenses/Pay-bills-in-QuickBooks-Desktop/m-p/2013....

On the other hand, you may run and customize a QuickReport to check the payment transaction and link it with the open bill. It's possible that the payment was not properly link when recording it to pay the bill.

Here's how:

1. Go to the Lists menu.
2. Select Chart of Accounts.
3. Click the drop-down for Reports, and choose QuickReport: Account name.
4. Set the date range.
5. Click the Customize Report button.
6. Under Filters, search Transaction Type, and you can select Payment only.
7. Search and filter Account.
8. To open any of the transactions listed, double-click the transaction entry in the report.

Additionally, you can go to the Vendor Center and open the vendor payment. Then, press Ctrl + H on your keyboard to show the transactions linked to the payment. 

That's it! This should help you link the bill to the vendor payment so it won't show on the Unpaid Bills Detail report. If there's anything else you need, drop a reply below. I'll be happy to answer. Have a great weekend!