Hello there, @Elizabeth 1.

I'm here to guide you in adding your invoices to a project. This way, you'll be able to track your income to effective manage your growing business.

The existing invoice was originally linked to the customer and not to the project. That's why it'll be removed once you link it to a project. To fix this, you can delete the invoice and link the Quote to the project.

1. Go to the Sales menu.
2. Select the Invoices tab.
3. Locate the invoice, click the drop-down arrow under the Actions column, then select Delete.
4. Go to the All Sales tab, then find the Quote. You can select the Filter drop-down to easily locate the transaction.
5. Double-click the quote, then select the project name under the Customer name section.
6. Click Save.

Once done, you can now create an invoice out of the quote. Just select the Create invoice button, then save. I've attached a screenshot below for your reference.

You can use the "job costing" feature to calculate your profits and cost by project. If you wish to track your project labour costs, calculate the hourly cost rate for each worker. For the detailed steps, you can check out Step 5: Track your hourly time costs section of this article: Track income, costs, and profitability by project.

Please let me know if you have other concerns. I'm just around to help.