It is common to use templates for invoices and avoid using papers nowadays. We provide these templates, so you can use and update them according your activity or product. Never forget that any invoice must contain data about recipient, amount of his payment, data about payment (bank account, etc.), and information about business, which provided service or product.
In fact, invoice represents by itself a list of specific services or products provided by business to business or client and payment the client owe to you. We can say that invoice is like a usual bill you used to pay each tax period.