On the 16th of each month, you'll get billed for the following month's box (if you're on the month-to-month plan), or once every 3, 6, or 12 months, according to the prepaid subscription option you’ve chosen. If you skip any boxes on a prepaid plan, your remaining boxes will simply move to the following month (your purchased boxes never expire). Your renewal will not go through until you have gone through all of your prepaid boxes.
However, please note that each month's renewal pays for the following month's box (e.g., the January 16th renewal covers the box shipped in early February, the February 16th renewal covers the box shipped in early March, and so on), so if the final box on your 6-month prepaid plan is shipping in early May, for instance, your renewal will go through on May 16th for June's–November's boxes.
Regular subscriptions renew automatically, but can be cancelled whenever you'd like, and you can skip any boxes you'd rather not receive simply by emailing us. Gifts do not auto-renew.