Court ordered custody has nothing to do with claiming a dependent on a tax return.
The tax law rules for a "Qualifying Child" dependent requires that child must have physically lived with you more than 1/2 the tax year and must be your son, daughter, stepchild, foster child, brother, sister, half brother, half sister, stepbrother,stepsister, or a descendant of any of them.
If the child that lived with you since March is not related to you in one of the above ways then you cannot claim the child as a dependent at all because the other the other type of dependent (Qualifying Relative) requires that that person lived with you the entire year plus other requirements if not closely related.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
