Within Teamwork, you can export invoices from a project to your FreshBooks account.
You will first need to enable the FreshBooks integration in your site settings.
In the Billing area of your project, select the invoice you want to export from the invoice list on the left hand side of either the open or completed invoices section.
In the bottom left of the invoice, you will have an option to Export Invoice.
When you select export, you will see the export options available. Select the Export to FreshBooks option, and click Export.
In the next modal, you will need to select a client from FreshBooks to associate with the invoice.
If you do not have any clients, you will need to create some in FreshBooks before you can export. Click Reload to see the newly added clients.
You can choose to add the Teamwork invoice to FreshBooks as a new invoice or add it to an existing one.
At the bottom of the modal, you can customize which invoice contents are populated.
Once you click Export, you will see a confirmation message with a link to your newly-created invoice.
Click the blue icon to the right of the invoice number to open it in FreshBooks.
For more information, see: Enabling the FreshBooks Integration for Your Site