Domestic partnership is defined by the U.S. Office of Personnel Management as two members of the same sex who are in a committed relationship, maintain the same residence and share in each other's financial obligations. If you are in a domestic partnership, it may be possible to claim your domestic partner as a financial dependent on your annual income tax return.
To be eligible as your dependent, a domestic partner must first and foremost have made a very small amount of taxable income; as of tax year 2013, the figure was $3,900 or less. In addition, the domestic partner must derive at least 50 percent of her total financial support from you and must be a citizen of the U.S., Canada, Mexico or a registered alien. However, because registered domestic partners generally report income as combined income, it is likely that you will need to file as a single individual to claim your domestic partner as a dependent. If a domestic partner is the only other person in your household, you cannot file as head of household -- even if your domestic partner qualifies as your dependent.