Husband claimed exempt for last 3 months of year. W2 does not include exempted income. Do I add it when doing my taxes? I know it needs to be taxed.

My husband claimed exempt because we was getting a lot of overtime, we needed the extra money.  It was from Oct thru Dec.  Well we knew we would have to pay the taxes come tax time.  But on his W2 the employer excluded the exempted income from box 1.  Do I just add it back in or do I have to use the number that is in box 1.  It is significantly less than box 3.