Do I just pay for the difference between two plans?
Great question! The short answer is yes, you would pay the difference. Annual payments are added to your account as a subscription credit, so the system would only charge you the difference owing to ensure that there is enough credit on your account for the remainder of your annual subscription period.
Note: Since apps/transaction/shipping fees exist as ‘pending charges’ until the next subscription invoice is issued, this means that any pending app/shipping/transaction fees will be included with the invoice when you upgrade or downgrade your plan. You can check out the Account Summary on the Accounts page in your admin to view any pending charges.
May I ask why you’re looking to upgrade your plan?