Payment processing occurs during registration and when you submit Test Reports to Water Suppliers that charge a fee. Typically this is done using the credit card that is stored on file.
You can view your existing credit card stored on file (with sensitive information redacted) in Your Account. You can get to this from the Home screen by tapping/clicking on My Account and then Edit Profile. The Billing Info button will display all of the details necessary to enter your credit card details.
1. Home screen
2. Your Account
3. Billing Information
4. Completed card will be shown if successful!