Thanks for letting us know, B_Marcil. It's important that you find the service that works for you regarding importing your invoices and their payments. At this time, there isn't a built-in function for importing invoice payments. While you can import invoices, manually adding the associated payments is the way to go to make sure everything is entered correctly. I'll include a few articles for you below that explain the options.
Otherwise, I encourage you to check out what other apps are available that can help you with importing your invoices and payments. Using the Apps tab allows you to search for what's available in that realm.
Here are the articles I mentioned. Don't hesitate if you have more questions!
