Hi there, EBG. You can easily change an invoice from the customer that's associated with a project without creating a new one. I'd be glad to provide you the steps on how to do it.

When editing the project, you'll need to locate the existing invoice that is assigned to that customer. Then, edit the invoice under the Action column.

Here's how:

1. On the left panel, click Sales.
2. Select Invoices. Then, locate the invoice you want to edit.
3. Under the Action column, click Edit.
4. Click on the customer dropdown. Then select the customer that has project on the side.
5. Select the appropriate project.
6. Hit Save and Close once done.

Additionally, you can personalize your invoices any time when you want to add information.

Here in the Community, we always find ways to solve your concerns. I'm here to help.