As well as getting nBill to create order records automatically when users submit order forms on your website front-end, you can manually create an order record for a client which will then be used by nBill to automatically generate invoices on a regular basis.
As well as getting nBill to generate invoices automatically - either when an order form is submitted, or when a recurring payment is due - you can also create one-off ad-hoc invoices whenever you like. You can choose to e-mail individual invoices to the client.
Income and Expenditure
nBill will typically create income records whenever it receives notification of an online payment through a payment gateway, but you can also add your own income and expenditure records, thus allowing you record all of your bookkeeping in nBill and to report on the data.