Anyone know how to create a invoice for direct ad sale?

I just had my first sale

[DNelly]

So I just completed my first direct sale for an adspace on my site, and I need to fax him an invoice. Does anyone know what this should look like? I got a basic idea but was hoping someone could point me in a better direction. Thanks.

PS. It's just for a flat rate for the month of April

[topr8]

an invoice is basically just like a letter!

you should include:
your name/address details
date
their name address
and the cost
an invoice number (if it's your first you could just make a number up or start at no1 whichever you prefer)
i'd also add a line like: payment due in advance of service starting.