Here is a reply from Alertpay:
If your customers are only paying for a product once, they do not need to create an account.
When they click on your “Buy Now” button, they can pay for your product/service with their credit card. At this stage they will be required to enter their personal information as well as their credit card information. Once they initiate a transaction, we automatically open an AlertPay account and send a validation email to them.
If they wish to pay for a product or service a fourth time, the customer must access the validation email, click on the validation link and use the temporary password we have provided in the email.
If they have successfully entered their password, they will be prompted to create a Transaction PIN and security questions/answers. When they have validated their email, they can have full access to their AlertPay account and make as many credit card payments as they have to without entering their information again.
