Nice to have you joined this thread, @accountant30.

I see that you've posted a similar question in the Community space and my colleague already responded to it. 

If you haven't read it yet, you can check it out via this link: https://quickbooks.intuit.com/learn-support/en-us/do-more-with-quickbooks/project-expenditures-not-a...

In case you need to add an existing invoice to a project, you can refer to Step 6 in this article: Set up and create projects in QuickBooks Online.

If you have any other concerns or questions about projects or with QuickBooks, you can always tag me in your reply. I'll be here to answer them for you. Keep safe!