Writing templates are widely available online. A Google search will lead you to websites that offer downloads of different templates. Some of them are even free. These prepared formats often come in predetermined categories and include sections like the title, introduction, list, and ending paragraph. All you have to do is fill up these sections depending on your chosen content.
Having finally designed the invoice template, you will have to print it. Here, again, you have some options. For one, you may simply customize your invoice template and print the invoice within your office, and submit them to your customer. You may even electronically transmit your invoice, using the email. At times, you may need to provide blank invoices to your servicing staff, enabling them to prepare invoices on the spot and to hand them over to customers for collecting payments. You may also consider having a combination of all these.