How to write a proper sales receipt for web development services provided to a client?

I have just taken on my first client and we have agreed to some terms and I need to get it into writing in the form of a receipt for obvious reasons.
Now I know the basics of a receipt:
1) It needs to define what is being sold/purchased
2) It needs to define the price paid for said goods/services
What I am doing is creating a new website for my client and providing hosting for the website. Does anyone have any advice for how a web developer should go about creating receipts for his or her…
How to write a proper sales receipt for web development services provided to a client?

See original post by Arson