I can point you in the right direction of a report that will show how much you've already paid a contractor. Follow the steps below.
Open QuickBooks.
Go to the Reports tab.
Select the "Standard" section.
Scroll down until you see the "What you owe" section. Note: I'd use this section of reports for your specific request.
On any of these reports, you can customize them to show different information than what's on the default report. Here's a link that can help you get the report of your desire: