Only for divorce orders that are dated in 2008 or earlier. For a 2009 or later divorce, the IRS will not honor the divorce order, only the form 8332. If your ex won't sign it, you may be able to take them to family court and get the judge to order them to sign, or be fined or held in contempt.
Frankly, I would rather negotiate a $2000 reduction in child support every other year; that way you get the same benefit without needing the other parent's cooperation.
