If you did not receive an email invoice, no matter where you ordered from, you are able to log in to your account and download an invoice.
If you ordered from HeadsetBuddy.com log in using your email address and password, or create a new account. Once your account is setup or your logged in, go to the Completed Orders page. From here you can print invoices.
Log into your Amazon account, go to Your Orders. Find the specific order and click invoice on the right side of the screen.