N.Y.C. Admin. Code § 15-114: § 15-114 Resignations and absences.

Any member of the department who shall withdraw or resign without the permission of the commissioner shall be subject to the forfeiture of salary due to such member. Unexplained absence, without leave, of any member of the uniformed force, for five days, shall be deemed and held to be a resignation by such member, and accepted as such.