You can integrate the Authorize.Net payment system into your online store through several add-ons.
Currently, there are two out-of-the-box Authorize.Net payment add-ons available in the X-Cart Marketplace:
Authorize.NET SIM enables accepting payments via the Server Integration Method. The SIM integration method uses the payment form hosted by Authorize.Net. When your customers click the "Place Order" button, the payment form opens. They complete the payment on the side of Authorize.Net and return to X-Cart afterward. It means that you can use a shortened PCI Self-Assessment Questionnaire during the PCI DSS compliance assessment of your eCommerce Website.
With this payment method enabled in your store, you do not need to worry about PCI-DSS compliance accepting payments from your customers as Accept.js sends payment data directly to Authorize.Net. This way, sensitive payment data does not ever reach your server. The process is seamless for your customers as they do not leave your site to make payments.
To accept payments with Authorize.Net, you will need an Authorize.Net account. If you do not yet have one, you will be able to sign up in the process of setting up the Authorize.Net payment for your store.
There is also an additional Authorize.Net payment integration available via X-Payments (information on using X-Cart with X-Payments is available here). This type of integration supports such payment methods as Authorize.Net AIM, CIM, and AIM XML and allows you to save credit card data for recurring orders securely. To use this type of integration, you will need an X-Payments account providing you with subscription-based access to X-Payments facilities and a connection add-on (aka "X-Payments Cloud connector") to link your X-Cart store to X-Payments. Detailed information on connecting your X-Cart store to X-Payments with the help of this add-on is available here.