Your invoices are accessible at all times via the Billing tab in your profile.
Step 1: Sign into your profile and click the Billing icon
Step 2: Click the Invoices tab
Step 3: Click the Invoice date you would like to view.
Step 4: Your invoice will look similar to the below. It will include the payment period, cost and the profile the invoice is for. From here, you can print and save to your computer.