Check boxes 3 & 4 on your W2. Box 4 should be 6.2% of box 3 up to a max of $8,537.40. So take the amount in box 3 and multiply it by .062. If box 4 is more than that you need to get a corrected W2 from your employer. But also go back and double check your W2 entries, you may have entered box 3 & 4 wrong. A lot of people who have asked this found they did enter an amount wrong.
Or check W2 box 12. You may have entered Code A by mistake.
A sure way to fix this is to delete the W2 and re-enter it. That may clear something out.
Or post back with the amounts in boxes 3&4.