When you approach your Usage Credit limit, notifications are sent in the product, and to the account owner’s email.
On Starter/Business plans, once you reach the limit, API document creation does not have a per-document overage rate. When your credits are used up, API document creation pauses. To resume, add credits to your plan or upgrade. For all other features, (Automations, Bulk Send, Forms, Zapier, Make, and other integration platforms), usage continues, and anything beyond your credits is billed as overage at the per-unit price on your current order form. If your order form has no per-unit price, you will be charged up to $5 per document created.
License upgrades are prorated based on the remainder of your current subscription term.