Unfortunately, any withdrawals that are taken from a deferred compensation plan, are taxable income at ordinary income tax rates in the year they were withdrawn. This is treated much the same as a withdrawl you would make from a traditional IRA account. Although there is not much you can do at this point to reduce the tax burden, you might be able to work out a payment plan with the IRS if paying the entire tax bill at once would be create a financial hardship. I wish I could have given you a brighter outlook, but that is just the nature of deferred compensation and the taxes that come with it.
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Thanks for the question and good luck to you in getting this worked out.