heres the pertinent section of the NEC

210.4 Multiwire Branch Circuits.
(A) General.
Branch circuits recognized by this article shall
be permitted as multiwire circuits. A multiwire circuit shall be
permitted to be considered as multiple circuits. All conductors
of a multiwire branch circuit shall originate from the same
panelboard or similar distribution equipment.
Informational Note: A 3-phase, 4-wire, wye-connected power
system used to supply power to nonlinear loads may necessitate
that the power system design allow for the possibility of
high harmonic currents on the neutral conductor.
(B) Disconnecting Means.
Each multiwire branch circuit
shall be provided with a means that will simultaneously
disconnect all ungrounded conductors at the point where
the branch circuit originates.
Informational Note: See 240.15(B) for information on the
use of single-pole circuit breakers as the disconnecting
means.