I'm looking at adding a three-way switch to a room. I'll probably drop the hot and neutral into Box #1, but 12/2/2 (hot, 2x travelers and a neutral) is fairly esoteric cable (nobody locally sells it by the foot) and it's pricey.
I got to thinking about it some, and was wondering if I need a neutral in Box #2 at all if Box #1 is covered. If not, I can easily buy 12/3 and just call it good.
Best Answer
No, you do not need to extend the neutral to all locations in a multiway setup
NEC 404.2(C) governs the provisioning of neutral at switch boxes (irrelevant parts snipped, emphasis mine):
The emphasized sentence applies to basically all multi-way setups you will run into in a house: it would be very strange indeed if you could not see what you are doing with the light from at least one controlling switch location.
Furthermore, the way multiway smart switches work only requires more conductors than fit in a /3 cable at the location of the "master" switch; a /3 is sufficient to connect the remotes to the master in all systems I have seen.