N.Y. Gen. City Law § 46
Every employing or master plumber carrying on his trade, business or calling in any city of this state shall register his name and address at the office of the board of health or the examining board of plumbers if so designated by local law of the city in which he shall conduct such business, under such rules as the respective boards of health or the local board of examining plumbers, in conjunction with the board of health of each of the cities shall prescribe, and thereupon he shall be entitled to receive a certificate of such registration, provided, however, that such employing or master plumber shall at the time of applying for such registration hold a certificate of competency from an examining board of plumbers.
N.Y. Gen. City Law § 46