Edit: here you go, directly from IRS publication 501, which explains the filing categories. Note that you must meet ALL three requirements.
"Head of Household
You may be able to file as head of household if you meet all the following requirements.
You are unmarried or “considered unmarried” on the last day of the year.
You paid more than half the cost of keeping up a home for the year.
A “qualifying person” lived with you in the home for more than half the year (except for temporary absences, such as school). However, if the “qualifying person” is your dependent parent, he or she does not have to live with you. See Special rule for parent , later, under Qualifying Person."
It's not illegal if you have been separated for 6 months out of that year and provided over 50%. Even if still "legally" married. You just have to have been separated 6 months.
Quoting RobinBright:
Illegal. Read the IRS.gov page that explains HOH. This is a prime example of why paying a tax service can be a huge waste of money.
Quoting Fairywings1223:
We get our taxes done and they always make dh hoh. :/
We have out taxes done professionally at H&R block every year and they always list one of us as HOH. So how is this illegal? And if it is why would so many professional well know tax preparers do it? They back you on every tax prep they do so I'm perfectly secure with how they file my taxes. What difference does it make when someone is listed as HOH anyway?
Quoting malibucj:It's not illegal if you have been separated for 6 months out of that year and provided over 50%. Even if still "legally" married. You just have to have been separated 6 months.



- RobinBright
on Jan. 12, 2013 at 6:27 PM