Filing Status

Married Filing Jointly
You can choose married filing jointly as your filing status if you are married and both you and your spouse agree to file a joint return. On a joint return, you report your combined income and deduct your combined allowable expenses. You can file a joint return even if one of you had no income or deductions. If you and your spouse decide to file a joint return, your tax may be lower than your combined tax for the other filing statuses
Married Filing Separately
You can choose married filing separately as your filing status if you are married. This filing status may benefit you if you want to be responsible only for your own tax or if it results in less tax than filing a joint return. If you and your spouse do not agree to file a joint return, you have to use this filing status unless you qualify for head of household status, discussed next.
You may be able to choose head of household filing status if you live apart from your spouse, meet certain tests, and are considered unmarried
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 .
If you qualify to file as head of household, your tax rate usually will 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.
How to file. If you file as head of household, you can use either Form 1040A or Form 1040. Indicate your choice of this filing status by checking the box on line 4 of either form. Use the Head of a household column of the Tax Table or Section D of the Tax Computation Worksheet to figure your tax.
Considered Unmarried
To qualify for head of household status, you must be either unmarried or considered unmarried on the last day of the year. You are considered unmarried on the last day of the tax year if you meet ALL the following tests.
You file a separate return (defined earlier under Joint Return After Separate Returns ).
You paid more than half the cost of keeping up your home for the tax year.
Your spouse did not live in your home during the last 6 months of the tax year. Your spouse is considered to live in your home even if he or she is temporarily absent due to special circumstances. See Temporary absences, later.
Your home was the main home of your child, stepchild, or foster child for more than half the year. (See Home of qualifying person , later, for rules applying to a child's birth, death, or temporary absence during the year.)
You must be able to claim an exemption for the child. However, you meet this test if you cannot claim the exemption only because the noncustodial parent can claim the child using the rules described later in Children of divorced or separated parents under Qualifying Child or in Support Test for Children of Divorced or Separated Parents under Qualifying Relative . The general rules for claiming an exemption for a dependent are explained later under Exemptions for Dependents .
Joint Return After Separate Returns

You can change your filing status by filing an amended return using Form 1040X.

If you or your spouse (or both of you) file a separate return, you generally can change to a joint return any time within 3 years from the due date of the separate return or returns. This does not include any extensions. A separate return includes a return filed by you or your spouse claiming married filing separately, single, or head of household filing status.

Separate Returns After Joint Return

Once you file a joint return, you cannot choose to file separate returns for that year after the due date of the return.