PayPal:
Via Email:
If you made your purchase using your PayPal account, you will have received a receipt from PayPal to the email address they have on file for your account. If you are unable to find the email by browsing for it, try performing a search. The receipt will have the following subject line and from address:
Subject line: “Receipt for Your Payment to Humble Bundle, Inc.”
From: service@paypal.com
Once you have located this email, look for the transaction ID in the Description area of the receipt.