I'm experiencing the same difficulty so adding my comment to the list of others. We have just started using CoConstruct as our project management software. It allows us to link our client and their project to the corresponding client data in quickbooks. We have many repeat customers with pre-existing payment histories. Without the ability to associate a pre-existing invoice with a newly created project; all the previous payment history for that client gets imported. This means for any client we've ever received a payment from, when we start a new project it shows 'X' amount of money already paid and completely messes up our financials. As a result we're not able to link, push or pull payment data from quickbooks for any client we've ever taken a payment from in the past. It's chaos.