Invoices in getSoapy

Invoices are automatically generated when a job is marked as done, according to the job cost.

If you've enabled the "Job marked as done" customer notification (see How do I change automatic customer notifications?) the customer will receive a message letting them know what they owe with instructions on how to pay if they've not provided an automatic payment method.

Invoices statuses

Outstanding
The invoice or part of the invoice has not been paid.
Overdue
The invoice or part of the invoice has not been paid, and it has been longer than the invoice lead time selected in More > Payments > Payment options.
Paid
The invoice has been paid in full.