Filing your U.S. federal income tax as head of household will generally result in a lower tax rate and a higher standard deduction than filing as single or married filing separately. According to the IRS, in order to file as head of household, you must be unmarried or considered unmarried, you must have paid more than half the cost of keeping up a home for the year, and you must have had a qualifying person who lived with you in the home more than half the year.
Qualifying persons include your children, grandchildren, parents, grandparents, brothers and sisters. There is an exception for dependent parents, who do not have to live with you in order for you to qualify to file as head of household. If you pay more than half the cost of maintaining a home that is the main home of your parent(s), you may qualify to file as head of household.
In order to file as head of household for having maintained a parent’s home, you would have to be able to claim an exemption for your parent as a dependent. This means that your parent must be a U.S. citizen, a U.S. resident, a U.S. national, or a resident of Canada or Mexico. So if your parent is a U.S. citizen, resident or national and lived in another country, you could qualify to file as head of household. Or if your parent lives in Canada or Mexico you may also qualify.
For other qualifying persons, the requirement is that the person must have lived with you in your home more than half the year. If you are a U.S. citizen or resident and live outside the U.S. you are generally entitled to the same tax benefits as if you lived in the U.S. So in this case, if you meet the requirements you could file as head of household.
According to the IRS, the requirement for a qualifying person to live with you in your home more than half the year is except for temporary absences. If either you or the qualifying person is away from home temporarily due to illness, education, vacation, business, or military service, you can still qualify to file as head of household. There must be a reasonable assumption that you or your qualifying person will return to the home. And you must continue to keep up the home during the absence.
If you are considered a U.S. nonresident alien and have to file a U.S. income tax return because you have income from sources in the U.S., the head of household filing status is not available. You would file using the appropriate status indicated on Form 1040NR.
If you become a U.S. resident, you would qualify to file as head of household if you meet the requirements. But according to the IRS, to file as head of household you would have to be a resident the entire tax year.
Sources:
Form 1040NR, U.S. Nonresident Alien Income Tax Return
Publication 54, Tax Guide for U.S. Citizens and Resident Aliens Abroad, IRS
Publication 501, Exemptions, Standard Deduction, and Filing Information, IRS
Publication 519, U.S. Tax Guide for Aliens, IRS