NM cable 3-wire to 2-wire?

[suobs]

Am I allowed to use 3-wire (plus ground = 4 wires) NM cable for a connection that only needs 2 conductors (+ ground = 3 wires)? If so, how do I flag the wire that's not being used? Can I just put a screw-on splice cap over it at both ends?

 

[user 4883]

how do I flag the wire that's not being used? No flag for unused conductors.
Can I just put a screw-on splice cap over it at both ends? Yes

 

[JoeD]

Leave it long in the back of the box at both ends and cap it. Do not cut it off as yo might find a need for it in the future.