Changes to a subscription such as upgrading or downgrading can result in prorated charges. For example, if a customer upgrades from business ($29/month) to enterprise plan ($99/month), they’re charged prorated amounts for the time spent on each option. Assuming the change occurred halfway through the billing period, the customer is billed an additional $35 (calculations below):
minus $14.5 for unused time on the initial plan (Business), and plus $49.5 for the remaining time on the new plan (Enterprise).
The prorated amount is calculated as soon as the API updates the subscription. The current billing period’s start and end times are used to calculate the cost of the subscription before and after the change