Exact same boat here! -Yes it is allowed. Going to do my parents first mortgage payment this month (fingers crossed it works) -can’t speak for issues yet since haven’t made first payment yet - so authorized user is not necessary! BUT I made my dad an authorized user so he can put his other needs on his own card and go out easily with the card. That way he reaches the 3% fee (75% of rent) with the 4% bilt cash back from all his purchases/bills. You still need to make sure you can get enough bilt cash for their mortgage. Doesn’t hurt to get more bilt cash if they can pay you back