Business Manager supports integration with several domain registrars and instant domain availability checking through your online store regardless of whether you're using one of the above registrars.
However, if you're using one of these registrars, your customers can purchase/transfer a domain name, pay for it, and Business Manager will issue a call automatically to that registrar's API to purchase/transfer the domain name and place it under that customer's account in your Business Manager for management (setting name servers, hosting records, etc.).
You can configure Business Manager to sell one, some, or all of the TLDs available through a particular registrar and charge your customers whatever price you want for their domain registration. Your account with your registrar will be charged whatever your standard reseller rate is for that given domain TLD. One of the clear benefits of this is that you can (for example) process ".com" sales through a certain registrar and ".ca" sales through another registrar, allowing you to use multiple registrars to make sure you're being charged the lowest possible price per TLD for the domains that you resell.
There are two steps in getting your system configured with one or more of the domain registrars through which you resell and to tie to appropriate TLDs to each of those registrars: