Switching from Monthly to Yearly subscription
If you still have an active subscription under your account, you can easily upgrade to the annual plan by yourself. The price will be pro-rated accordingly based on your unused portion of the current monthly subscription. So the earlier you upgrade, the more discount you will get.
First, go to https://leetcode.com/subscribe, click on Subscribe on the Annual plan, then select your payment method, and click on the Continue button.
On the next page you should be able to see the pro-rated amount for your upgrade, as shown below.
Please note that we are unable to convert your past monthly premium subscription to annual premium subscription and charge you the difference. The pro-rated amount is only based on your unused portion of the current monthly subscription.