My boss is very good about getting our W-2's to us quickly, as is U.S. Bank about getting me my mortgage statements for year-end. I have used Credit Karma Tax the last 3 years without incident, and did the same this year. Here's what happened: Credit Karma lets you file Federally before it's officially "open", so I punched in my info and submitted. The refund looked right to me, everything seemed fine. I have a VERY easy tax situation: one job, single, one property, no investments or other income. Return was processed, accepted, and refund issued from the feds. At that time, Credit Karma was not accepting MN returns yet. No big deal, they're always delayed. I waited until filing was open, and re-submitted based on the information already entered plus a few state-specific questions. Much to my shock, it reported that I owed the state $4,100 in tax! I almost hit the floor in shock, all the while KNOWING that there was a mistake somewhere. I claim 0 dependents and over-pay every year (I know, I know, leave me be) so there's no WAY I owe the state a dime. I begin frantically looking back through the process, trying to find out where I goofed, and then bam. I never filled out the state tax portion of my W-2 on the online form. Somehow I was able to not only continue with my return, but the fed's accepted it! I can't believe this didn't get flagged somewhere... how in the world could I report high 5-figures of income with absolutely no state tax paid? Or does the fed not look at things like that? Obviously, there are states with no income tax, but MN isn't one of them. Maybe I'm expecting more of the system than I should... Anyways, I fixed my mistake, submitted my state return (which is now a $360 refund), and filled out form 1040-X which I will promptly mail to the IRS. I just hope I filled it out correctly... there was only a few adjustments to be made to AGI and such. In the end I'm due an additional $451 from them, so it's kind of a nice surprise. I just hope I don't get some random audit out of all of this. That's the last thing I need... no, wait. A $4k tax bill is the last thing I need. /rant, lesson is: ALWAYS DOUBLE CHECK YOUR WORK, KIDS!