Why would it say my daughter has already been claimed when I know she hasn't been? My ex wife listed her on her taxes but did not claim her as a dependent.

[Anonymous]

if the ex-spouse listed her on her tax return it's likely in the dependent section.  she may have to amend to remove her.  because she in effet claimed daughter, you must now paper file.  

[Jmartax]

If your Ex wife put your daughter on her tax form, she must have answered some questions incorrectly. She should not have listed her at all so the the program sees her as a dependent.

You cannot claim her.  You may get your Ex to file an amended form 1040X.  If she doesn't, you cannot take the deduction.