Invoices total up Debt/Credits, and are sent to your Client. Invoices can be "generated" to file, picture, PDF, or email for presentation to your client. You can generate invoices with different built in templates, or create your own template.
Studiometry can automatically alert you of overdue Invoices, just set a due date and check the "Alert When Overdue" checkbox.
To create an Invoice, select Project Menu > New Invoice, or click the plus (+) button below the Invoice list in the main window.
You may then select which Debt/Credits to show in the Invoice, which Invoice Template to use, which Contact to Invoice To, and the Invoice Currency.