Hi @Cherokee99,

I can assist you with your query on how to add an existing invoice to a project. 

You'll have to open the invoice you want to add to a project.

Here's how:

1. Highlight the Sales tab.
2. Select Invoices.
3. Search for the correct invoice, then click to open.
4. Customer drop-down menu, select the project in question. 
5. Hit Save and close.

This option is unavailable for bill transactions, though you can add expenses to projects. You can apply the same steps above. You only need to open an existing expense, then change the Payee column to the correct project. 

If you have other queries about the Projects feature, take a look at this article: Projects FAQ. It has a list of common questions about this feature, as well as related links for it.

Let me know if you have other concerns. Leave a comment below, and I'll get back to you.