if you want to apply a payment from GT, you need an invoice.
i make an invoice template, its easy to use.
:o
http://www.aynax.com/freeInvoiceTemplate.php
I just used some BS Word document for the first few weeks till they put me on weeklies.
I invoice EWA every week with an email that lists my AID, revenue earned, the time period and when I expect payment. That is all you need to do. Don't worry about the format. Just give them the relevant information and they will pay.
guys, use freshbooks.com for invoicing, it is badass and its free for up to 3 clients. you will thank me later.