From the TrueRev dashboard, navigate to the Contracts tab.

Select and open the contract associated with the invoice you want to edit.

Go to the Billings tab.

Find the invoice, click the three dots, and select "View Invoice."

In the invoice details, click "Edit."

Make the necessary updates, including customer details, quantity, and rate. You can also add or delete invoice lines (unbilled products).

Click "Save" to apply the changes.