The requirements, per some stuff we saw from the National Advancement Team, are posted first now on scouting.org. Then, they are incorporated annually into BSA requirements #33015.
Guide to Advancement is the adult book for how to implement the method, nationwide. Requirements is the adult and youth book which lays out what has to be done, rank by rank, merit badge by merit badge, across the programs of Scouting.
John-in-KC's post in 2016 Guide To Advancement? was marked as the answer