If your taxable income is $48,000, your income tax should be $5,382 for MFJ. If you paid in $4,600, you will owe an additional $782 in income tax. Some questions that need to be addressed: (1) Did you have any self employment income? if so, this income and the self employment tax needs to be added to your return. This will increase your income tax due. (2)Did you apply for health insurance through the marketplace site in late 2017? If so, you should receive a 1095-A and data from the 1095-A needs to be entered in your return. If you failed to enter this data, it will increase your tax due amount. (3) Finally, check over all your data entries to be sure you have entered all the data correctly.
