When you upgrade from annual Premium to annual Pro;
- You will be charged for the upgrade amount immediately, which is proportional.
- Your account will upgrades to Pro immediately.
- The renewal date will stay the same as the original subscription.
The amount charged is proportional and is calculated by working out how many days left of your Premium subscription there is minus the cost of the Pro for this period.
Example 1: User subscribed to annual Premium, 20 days before the renewal date they upgrade to Pro. They will be charged = $4.48 for the last 20 days. They will then be charged $139.99 on the renewal date.
(Annual Pro = $139.99 / 365 days (1 year)) x 20 days (days left till the end of the subscription) = $7.67
(Annual Premium = $59.99 / 365 days (1 year)) x 20 days (days left till the end of the subscription) =$3.29
As she already paid for Premium for the year upfront.
$7.67 - $3.29 = $4.38