After logging in to Socrative through the Socrative Website, click on your name at the top right corner and click Profile.
In the Account header, you can view your account details. (Please keep in mind the Account tab is only available on the web version of Socrative.)
If you're using the Basic version of Socrative, you'll see the message below and a Learn More link that outlines more information on Pro:
Check out the plans page for more information on Pro and pricing information! You can also click on Upgrade if you're ready to purchase or have a license key ready to use. Please note, only credit cards are accepted for individual licenses. If you have 3+ teachers interested in Pro, please contact sales.
If you already have Pro, you'll find your subscription details here. You'll see a message like below:
Your license key will be shown, the expiration date, and an option to toggle on/off auto-renew (blue means it's turned on). You can also renew your license here using the Renew License button. If you need a copy of your receipt, you can have it emailed to your account or downloaded to your device.