After you have successfully activated the Sales Management feature.
Action: Manage sales -> Create invoice.
In the customer screen, enter your information
After entering customer information, click [Next] icon to add services
At the [Add Service] screen, enter the number of services and then click [Save] to save the service information
To pay for the service, Click icon [next] to make payment
On the invoice screen, select the payment form and the currency of your choice. Click icon [Add payment] to pay
Click [Save] to save the bill
Invoice was successfully paid