Now that you've established that your child is either a qualifying child or a qualifying relative, the remaining three tests are actually pretty easy:
- The dependent taxpayer test: If you (or your spouse, if filing jointly) could be claimed as a dependent by any other person, you cannot claim anyone else as a dependent -- even your qualifying relatives or qualifying children. (Of course, the good news is that if someone else can claim you as a dependent, you can do to them what your adult children are doing to you. Be considerate and pick up your wet towels off the floor, won't you?)
- The joint return test: If your child files a joint return with someone else, you may not claim your child as a dependent, unless the joint return is filed only to claim a refund.
- The citizen or resident test: You cannot claim a person as a dependent unless that person is a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico. (There are exceptions for certain adopted children.)
So provided that your child is a qualifying child or qualifying relative, you and your spouse are not the dependents of anyone else, your adult child is not filing a joint return, and your child meets the citizenship requirements listed above, the answer is yes, you can claim your adult child as a dependent on your tax return.