You don't have any control over what someone else does on their own tax return, so there is no way for you to block what someone else may do.
File your return with the correct information and you'll need to let IRS work it out on their end. That non-custodial parent will need to provide a Form 8332 to IRS showing that YOU released the child to them, in order for them to be able to claim that child....if you didn't sign an 8332 for that non-custodial parent, their claim will be denied by IRS.
♪♫•*¨*•.¸¸♥Lisa♥ ¸¸.•*¨*•♫♪
