Authorize.Net CIM: Multiple identical payment profiles for a customer profile

Authorize.Net CIM enforces a strict limit of 10 payment profiles per customer profile that gets stored in the Customer Information Manager. Keeping this value as low as possible by merging identical profiles is typically how Authorize.Net will handle this information. Authorize.Net will handle this automatically and ensure any identical profile (exact address, phone number, and card data) are merged into an existing profile if the customer is not using an existing stored card in Magento. Existing stored cards will always map to an existing profile, and so will not lead to duplication if a customer selects an existing stored card from their account and does not change the address information.

If you are seeing what appears to be multiple payment profiles that look identical, either there is some information that is different or Authorize.Net decided the profiles did not warrant a merge. Differences can be actual data differences, such as an altered address, phone number, or any changes to the card data. Authorize.Net can also allow itself to store duplicate profiles, and there is no controlling when Authorize.Net decides to do this or not. This means that it is not possible, via API or any other means, to fully prevent all cases of identical payment profiles.

The best solution for preventing this is to require customers to login to use the checkout, and to disable the configuration setting "Allow card to not be stored". This will help ensure all customers are always able to see their last used payment method and their stored addresses to help curb any possible data differences.