When you are logged in to your account, click on the tab in the upper right corner of the page that has your name on it. In the Account section, go to Receipts to view your monthly invoices. Click on the Date link for the corresponding charge to view and print the receipt.
If you need a VAT number, Tax ID, or any other text to show on your receipts, go to the Billing Info page and you can enter this information in the option field at the bottom of the page. This information will show up on your receipts. Only Admins can update Billing Info.