Within Teamwork Projects you can mark logged time as billed.
A time entry is marked as billed when it has been added to an invoice and the invoice completed.
In the Billing area of your project, select the Unbilled Time tab.
Drag and drop
Hover over a time log to reveal the move icon to the left. You can then click and drag the time log over to the invoice on the left to add it to it:
To drag and drop multiple time logs together, select the checkboxes to the left of each time log first. When you then drag and drop, all selected time logs will be moved:
Select an invoice
Once you have ticked time logs, you can use the 'Move Items' button to select a specific invoice to move them to.
In the invoice modal, you can either select an existing open invoice to move the time logs to, or create a new invoice for them:
For more information see: Logging time in the time area of a project