Why not? What credit/deduction do you believe you should be getting that you are not getting? What amounts are you seeing in your documents and tax return that make you think your refund is not correct?
We cannot see your return--provide some details.
And... have you entered EVERYTHING yet? Some documents you need do not arrive until late January or even February. Are all of your W-2's entered? They all have to be on the same tax return.