You may still be mailing paper invoices or you may be doing all your billing and payments over the internet, either using a website that accepts charge cards or an online payment system that uses email like PayPal. As a freelancer, this affects the part of your invoice that lists how you want to get paid. You may even offer your client a variety of payment options, and all of those should be mentioned on your invoice.
One option for receipts is to simply mark your billing or sales invoice as paid and send a copy to the customer. But if you need a detailed receipt for your business, this template allows you to track payment methods for your records while providing clients with their own receipt.