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Tax matters incident to divorce are more involved, especially since the joint filers mow have different interests.
There may be a couple of ways to minimize or escape the exposure to the tax debt for your friend.
An innocent spouse request allows IRS to consider your friend's involvement in the tax issue, and offer relief. Form 8857 (IRS discusses the form at http://www.irs.gov/Individuals/Innocent-Spouse-Questions-&-Answers) can be used to request relief.
An injured spouse allocation would allow for refund relief when the joint return creates a refund that is used to pay a debt of the other spouse. Depending on the circumstances, this could be usable.
The best thing to do is have your friend consult a tax professional, who can review all the facts, and the divorce decree, to determine the best course of action. Some decrees specify if a spouse agrees to cover any joint tax debts. If so, IRS does not honor those agreements, but your friend would have grounds to go back to court and seek relief from the 'ex'.
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Thanks for the information. Is her unemployment benefit subject to income tax? Thank you!
unemployment is taxable (line 19, form 1040).