When purchasing or renewing a Socrative PRO license, your receipt will be emailed to the address on file for the account.

Pro license purchasers may access receipt for the most recent transaction at any time in their account. Login to Socrative, click on your initial in the top right corner and click Profile. 

In the Account header, you'll find more information on your Pro subscription. 

At the bottom of the page, you can select to have your most recent receipt emailed to you or downloaded to your device.