There are a couple of distinct types of recurring invoices.
If you need to split your booked amount into equal portions and send the same invoice at regular intervals:
Set up the deal and product booking. Make sure the product booking amount is a multiple of the number of invoices you'll be sending.
Continue to the billing schedule.
Select the product. Recurring is the default billing schedule type.
Fill in the regular invoice amount, how often to bill, when to send the first invoice, and how many invoices to send.
Click the "save" button
As the invoice schedule dates arrive, you'll get reminded to review and send them, so you don't need to remember or track that on your own.
If you have a "no end date" deal and want to send the same invoice at regular intervals (similar to a cell phone service contract):
On the deal dates page, select auto-renew and set the renewal period to the same frequency at which you want to send the invoices.
On the booking page, expand the product details and check the "Auto Renewal" box.
Setup billing to use custom and send the full amount on the invoice.
When the deal "renews", you'll be able to send the same invoice again.
Yes, we realize it's awkward, clunky & not at all intuitive — we're working to get this improved in the next release.