When you change plans in the middle of a billing period, you are not charged a full new plan price and you do not lose what you already paid. Stripe calculates the difference for the days that remain and charges only that. The resulting line in Billing history carries a 'prorated' label.
A worked example. You are on Starter monthly and upgrade to Pro on day 15 of a 30-day cycle. Roughly half the Starter payment is still unused, so it is credited against the Pro price for the same fifteen days, and you pay the difference. The next renewal is a normal full Pro charge.
The same mechanic applies when you switch billing cycle mid-term, and when you move between volume tiers.
Two consequences that surprise people, both harmless:
- The amount will not match any price on the pricing page, because it is a partial period.
- Your renewal date does not shift. Proration adjusts money, not the calendar.
Every prorated charge has its own receipt in Profile → Billing, so an accountant can reconcile the odd amount against the plan change that caused it.