Hi there, Natasha.
To retrospectively change an entry on an invoice to a billable expense in QuickBooks Plus, you can follow these steps:
- Go to the Expenses menu and then Expenses.
- Find the expense that you want to make billable and click on the View/Edit button to open the details.
- Mark the Billable option.

- Select the customer or project.
- Click Save and close.
Once you have made the expense billable, you can then add it to an invoice by following these steps:
- Go to the Sales menu and then Invoices.
- Find the invoice that you want to add the billable expense to.
- Click the dropdown arrow under the Action column and select View/Edit.
- Click on the Add to Invoice button in the top right corner of the screen.

- Select the billable expense that you want to add to the invoice and enter any additional details, such as the quantity or description.

- Click Save and close.
Additionally, you may utilize the Projects feature in QuickBooks Online that allows you to organize all the transactions related to a specific job or project in one place. Using this feature, you can determine the profitability of each project.
Please don't hesitate to reach back out here if you have any other questions or concerns. The Community is always here to help. Take care always.