Event registrants need to be able to apply overpayments on an account (such as created when they cancel an event registration after payment) to a new registration. Currently, they can see the overpayment until they register for a new event, at which time the small on-screen overpayment notice disappears. Ideally, they should be prompted "Would you like to apply your account credit balance (overpayment) to this invoice?" and be able to pay any remaining invoice balance via the online payment method.