For small businesses, they track the basic cardmember's SSN to decide whether limitations apply, e.g., the aggregate 4 revolver for many cardmembers. In other words, you can have a gazillion LLCs and/or TINs, but your limitations will be predicated on your SSN as a basic cardmember which includes both personal and business credit lines. There's no limitation (where I'm aware of) on how many AUs you may on with on LLCs where a business partner is the basic cardmember, though any partner with a significant interest and his/her associated SSN must be disclosed during each application.