Marital Deduction Requirements

Filing a joint return might result in a so-called marriage tax penalty.

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Your marital status plays a key role in determining how your income is taxed. Married couples are the only taxpayers who are permitted to file a joint federal income tax return. Although married couples are not required to file jointly, marital deductions mean that filing a joint return often results in a lower combined tax obligation than filing separately . Whether you are eligible to file as married depends on whether you are considered married by the IRS for federal income tax purposes.

Time Frame

Your marital status as of the last day of the year determines your marital status for the entire year, at least as far as the IRS is concerned. If you were married on Dec. 31, you are entitled to file your taxes using either the married filing jointly or married filing separately filing status for that tax year. If you wait until Jan. 1 to get married, you'll have to wait until the following tax year to claim married as your filing status.

Legal Union

While a number of states have legalized same-sex marriages, the IRS recognizes marriage as the legal union of one man and one woman. If you file a joint return, you can claim the joint return standard deduction, which was $12,200 as of the 2013 tax year. You can claim a personal exemption for yourself and another exemption for your spouse, but when filing a joint return, your spouse is never your dependent.

State Law

The IRS looks to state law to determine whether you are legally married as of the last day of the year. The IRS considers you to be married if you are legally married and are living together as husband and wife, or if you are living together as husband and wife in a common law marriage that is recognized by the state. You can still claim the marital deduction if your spouse died during the year and you did not remarry before the end of the year. The IRS considers you to be married, even if you are separated but have not received a legal divorce.

Disadvantages of Filing Jointly

While filing a joint return often results in a lower combined tax obligation, once you both sign the return, you each become liable for all taxes due, regardless of which spouse incurred the tax obligation. You don't always pay lower taxes by filing jointly, particularly if one spouse has significant itemized deductions, so it makes sense to figure your taxes both ways, then file using the status that provides the lowest tax obligation. If you file separate returns, you will be responsible only for your own taxes, but you'll lose certain tax credits and deductions. For example, you typically can't take the credit for child and dependent care expenses, the earned income credit or the credit for adoption expenses.