Often times you correct it with more paper work. One year, my foreign tax deduction didn’t get filed for some reason (I was doing my own taxes by hand and sending in the forms), so I was hit with a huge tax bill of $30k or so. Then I found out I handled my non-resident wife wrong, so amend 1040X wait for ITIN, etc…it was kind of a mess. I wound up ahead, the IRS owing me instead. They were quite courteous about it on the phone.

This is my experience as well. The IRS generally knows that mistakes happen, and they generally don't really seem interested in criminally punishing small things. Normally they assess a small penalty payment at worst, and set you up with a payment plan if you don't have the money.