If you are filling a joint return, I assume you and your spouse had income that was reported to you on a W-2. You need to review the taxes withheld in box 2 of each of your W-2's and be sure the amount of tax withheld as identified on line 64 of form 1040 (will be a different line number for form 1040A) is equal to the sum of the taxes withheld as reported in box 2 of your W-2's. If the numbers are different, then I suspect you made a data entry error when you entered the data from box 2 for each W-2. If the numbers are the same, you probably did not have enough tax withheld from your earned income during the year. This may be the result of different exemptions reported on your return or different credits claimed between 2015 and 2016. If this is the case, you should talk to your employer and adjust your W-4 exemptions so that more tax is held out each pay period for 2017 or you will have the same problem on your 2017 return.
