What you have to do in this circumstance is print your return and file it by mail. When the IRS receives two returns each claiming the same dependent, they will contact each taxpayer for supporting information. Then they will decide who is legally entitled to claim the dependent. Winner gets the claim; loser gets a bill for additional taxes (and penalties, if any).
The IRS rule is that the right to claim a dependent child belongs to the custodial parent, which the IRS defines as the parent with whom the child spent the greater number of nights during the tax year.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
