I have a question relating to this.
I recently authorized my gf to use one of my cards so that she could build credit history. However it didn't ask me for her SSN or anything like that.
Is it even building history or her or no?
My wife (fiancee at the time) had zero credit history about 3 years ago and had to get a secured capital one card with a $200 CL. She never asked for an increase or to make it unsecured. About 1.5 years after getting that card, I added her as an authorized user to my new card with an 8500 CL. They never asked me for her SSN, however it does show up on all 3 of her credit reports. Mine as "I" for individual, hers as "A" for authorized user.
She did not see a jump in score, but she was already around a 740 Fico at that time. I cannot attest to how much it would've helped her score if she was at a much lower Fico to start. However, I believe that it helped her credit look better even though no score bump. She applied for a credit card on her own about 6-8 months later and got a 6k CL. Not bad for starting with a secured card of 200 CL about 2 years prior.
So to make a long story short, it will help her credit, just not sure how much. Just make sure it is reporting to the CRs.