A customer/user record can be an affiliate if two conditions are met:
The 'IsAffiliate' box is checked – the customer can set this by applying to become an affiliate through the 'my account – affiliate referrals' section, or you can set it manually.
The affiliate commission is set above 0% - this can only be done by a store admin on the back end of Kartris. In this way, each affiliate must be manually approved by an admin before their relationship with the store is confirmed and active.