Is an ex-spouse only responsible for one half the taxes on a return with delinquent taxes?

I have been asked this question before.  The general answer is that a spouse owes all of the taxes because he signed the return.  For a joint return the signers are jointly and severally liable for the tax.  This means the IRS can collect the entire tax from either or both, but the entire amount is only collected once. If the divorce order says he is responsible for half or none of the tax and he has to pay it, his remedy is in the Family Court.  The IRS does not have to follow state court orders.  If the ex-wife earned all the money for those returns, your husband might be eligible for Injured Spouse relief.  If the IRS agrees, he would be absolved from paying the tax.