If he received it in 2016 then it "should" have been included on a 2016 W2.
But if the employer isn't going to issue anything until 2017, then you will need to wait to report it in 2017, especially if withholding is involved.
♪♫•*¨*•.¸¸♥Lisa♥ ¸¸.•*¨*•♫♪