To claim an adult as a dependent, you must provide more than half their support, and they can't have more than $4300 of taxable income. If the adult is not your parent, grandparent, or aunt or uncle, they must also live in your home the entire year. Social security does not count as taxable income for the income test but it does count as support for the support test. You may need to determine the person's total financial support (room and board, clothing, travel, entertainment, medical, etc.) and count their contributions (from social security, savings, etc.) and your contributions, to see if you pay more than half.
