After you file

You need to look at the entries from line 24 to 31 on your tax return form 1040. Then compare them to the same lines on last year's tax return. On these lines you will see your Total Tax (line 24) and the deductions from that tax (lines 25 to 32.) That is where you will find the difference between this year and last year, and that may explain why you owe taxes this year.