Yes, you can.
We don't ship orders with printed invoices, it's not something most people have a use for so would be a huge waste of paper. It's easy to get one if you need it though.
When you complete an order, the confirmation page has a button allowing you to print the invoice, but if you missed this when placing the order, you can print the invoice from your online account.
The landing page when you log in lists previous orders (if you're already logged in you can reach this page by clicking the "Re-Order" link at the top right of the screen).
By each order number is a "View Invoice" link, which allows you to view or print an invoice.