My worst story is when two years after the fact, I got a notice that I was being audited by the IRS and I owed them like $2500. After panicking, I realized it was because THEY didn't count my student loan interest deduction. So I spoke to a human on the phone who was like ...yeah, you're right, don't worry, that was a stupid mistake on our part ...but I still had to go back and forth in the mail for months freaking out every time, even though the IRS guy right there on the phone the first time admitted it was an IRS mistake and I had done my taxes correctly.