The white wire used in a switch loop wired with a two-wire cable like Type NM must be re-identified. This is normally done with black tape.

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This is true. The white wire in a switch loop must be re-identified to a color other than white, typically with black tape, to indicate that it is a switched hot wire rather than a neutral wire. This is required by the National Electrical Code (NEC).

The White Wire Used in a Switch Loop Wired with a Two-Wire