Payments

Greetings, @Chantal787. 

It's great to see a new face on this thread. Let's work together to help you add an existing invoice to a project within your QuickBooks Online account. 

If the invoice is unpaid, review the steps below to add the invoice to the project: 

1. Go to Get paid & pay and select Invoices.
2. Find and select the unpaid invoice.
3. Select Edit invoice.
4. Select the Customer dropdown. Then select the project.
5. Select Save.

For further details, check out this guide: Add existing invoices to QuickBooks Online Projects. 

I hope this helps and does the trick for your business. I'm only a reply away if you need me. Take care!