Refer to the section in Publication 555, Community Property Laws Disregarded.
You may need to seek the help of a tax professional.
**Mark the post that answers your question by clicking on "Mark as Best Answer"
Assuming your current separation will lead to a more permanent end, you should let your Lawyer earn the money you pay them, and they can get the information for you - generally with no problem. Once the non-cooperating party realizes they are in violation of federal or state law, they tend to do what that law requires of them.