Originally Posted by AAdamE

You need an AUs full social and the trade line goes on their credit. I have the Citi AA Executive card and there is no AF for up to 10 AUs who get admirals club with 2 guests. Being a good human, only my immediate family are AUs but some were uncomfortable that they needed to provide a social & the tradeline going on the credit report (even though I don't ever carry a balance). Still it shows up as a new account - so it won't show past payment history, but some highly sensitive people might not want a "new" account on their credit (like if you're about to get a mortgage). Charge cards report differently (since there's no preset spending limit). Lastly, Chase has been known to shut ppl down for "piggybacking" or adding AUs with 0 spending power in exchange for a good tradeline on the others credit. Usually set off by adding AUs with different addresses / last names. Not sure if AMEX cares about that.