Glad to see Taxoh and Taxiowa....  I would take anything they say on this subject as gospel.....

Years age (like > than 10) I lost a lengthy argument to them on this subject because I couldn't wrap my head around the huge loophole the IRS left standing........ I even went as far as to speak with a senior agent in the EITC section at the IRS and used the following example.

He and she are unmarried living together with two naturally born children.......  He owns a small corp and receives 300K W2 wages. She also receives 12K in W2 wages from the same Corp for whatever (business) services she performs. She can claim single with the children and the credits.  He must also file single. But, if they were married it would be  MFJ and goodbye credits