Per IRS Publication 501 Dependents, Standard Deduction, and Filing Information, page 8:

Head of Household

You may be able to file as head of household if you meet all the following requirements.

1. You are unmarried or considered unmarried on the last day of the year. See Marital Status, earlier, and Considered Unmarried, later.
2. You paid more than half the cost of keeping up a home for the year.
3. 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 doesn't have to live with you. See Special rule for parent, later, under Qualifying Person.

If you qualify to file as head of household, your tax rate will usually be lower than the rates for single or married filing separately. You will also receive a higher standard deduction than if you file as single or married filing separately.

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