I cashed out my 401K from my old job in June. The mandatory 20% ( federal taxes) was taken from the amount I received. I know I also need to pay state taxes, and the 10% early withdrawal fee. Do I just send the state a check ( how would I figure the amount ? ), or just wait until I fill out my state tax form at the end of the year ? As far as the early withdrawal fee goes, who do I send that to ? And, is there anything else I'm obligated to pay besides these ?

Dlink:

You will get a Form 1099-R in January which documents how much was withdrawn and how much was withheld for taxes. That income is reported on both your federal and state income tax returns as ordinary income.

You will need to file Form 1040 in order to report the income and the 10% early withdrawal penalty.

In effect, you need to do NOTHING until it is time to file your tax returns.