Only married couples are able to file a joint federal tax return, and for federal income tax purposes, a married couple means the legal union of one man and one woman. While you can't file a joint federal income tax return with your domestic partner, regardless of whether he is disabled, you might be able to claim him as a dependent, if he meets the IRS' four tests as a qualifying relative. If he does, you can take an exemption for him when you file your federal income tax return, which will reduce your taxable income.
Not A Qualifying Child
If your domestic partner is another taxpayer's qualifying child, you can't claim him as a qualifying relative, even if that person meets all of the IRS' other tests. There is one exception to this rule. If the other taxpayer who could claim your partner does not file a tax return because she is not required to do so, or isn't required to file, but does so only to receive a refund for taxes withheld, the IRS doesn't consider your partner to be that taxpayer's qualifying child.
Member of Household
If you want to claim your disabled partner as a qualifying relative, she must have lived with you as a member of your household, in a relationship that does not violate local law, for the entire year.
Your ability to claim your disabled partner as a qualifying relative is limited by your partner's gross income. Your partner must have received less than $3,800 in gross income for the 2012 tax year to qualify as your relative. That includes both earned and unearned income, but it does not include tax-exempt income.
You must have provided more than half of your domestic partner's total support for the year. The IRS considers such expenses as food, housing, clothing, health care, education, transportation, recreation and other common necessities to be part of support.
Mike Parker is a full-time writer, publisher and independent businessman. His background includes a career as an investments broker with such NYSE member firms as Edward Jones & Company, AG Edwards & Sons and Dean Witter. He helped launch DiscoverCard as one of the company's first merchant sales reps.