I'm not sure what you mean by duplicate registration. You can configure KonaKart to allow a customer to checkout without registration. You can also configure KonaKart to allow a registered customer to checkout without signing in although in this case he / she won't see the order in the order history. This second feature was added in version 8.8.0.0 . Here are some details https://www.konakart.com/javadoc/server/com/konakart/app/CustomerRegistration.html#setAllowMultipleRegistrations(boolean)