In order to pay with an invoice, please start the registration process.
When you get to the Payment page, please turn off the Monthly Billing option as seen in the attached screenshot below.
Once you turn off the Monthly Billing option, it will appear gray, and you will then get an option to choose the duration of your course access:
Once you choose the duration of your course, your registration and payment process will continue as normal. You will soon be enjoying your new course!