The IRS is at least somewhat flexible about whom you can claim as a dependent. An adult can qualify, particularly if the adult is your parent. However, some criteria apply. You can't claim your mother if she's supporting herself, but you may be able to do so if she's residing in an assisted living facility. If you're paying for the facility, you may be able to deduct the costs of that as well.
Claiming Your Mother as Your Dependent
Although many dependents must live with you to qualify, your mother does not. However, if she's married, she can’t file a joint tax return with her husband, unless it's only to allow her to claim a refund. She can't earn more than the dependency exemption for the tax year in which you want to claim her, which is $3,800 in 2012. Social Security benefits typically don't count toward her income, but interest from investments and other unearned income does, so this can be a tricky qualification to meet. You must also pay more than half of her living expenses, and if she uses Social Security to pay some of her expenses, Social Security does count for figuring the portion of her expenses you've paid.
Qualifying Medical Expenses
The IRS recognizes assisted living expenses as qualified medical deductions when you pay them on behalf of a dependent. If you're also paying toward your mother's Medicare coverage or other insurance for long-term care, you can claim these payments as well, but on a graduated scale depending on your mother's age. The older she is, the more of her insurance payments you can deduct. If your mother is in an assisted living facility for medical reasons, the entire expense is deductible. However, if she simply prefers to live there rather than on her own or with you, you can't deduct the portion of the costs attributable to lodging and meals.
Medical Expenses Vs. Standard Deduction
You must itemize deductions on your tax return to claim your mother's assisted living costs. You can't take the standard deduction of $11,900 in 2012 if you're married, $8,700 if you're head of household, or $5,950 if you’re single. If your mother's expenses are exorbitant, you might be better off itemizing, because the expenses would add up to more than the standard deduction you qualify for. However, you can only use the portion of her expenses that exceed 7.5 percent of your adjusted gross income. This means that if your AGI is $125,000, you must deduct $9,375 from the assisted living payments you made. You can only claim the balance as a deduction.
If your mother does qualify as your dependent, you can also claim a $3,800 exemption for her in 2012, in addition to a percentage of her assisted living costs. However, if she just misses qualifying as your dependent because she earned too much, or because she filed a joint return with her husband, you may still be able to claim her medical expenses if you paid them, even if you can't claim the dependent deduction. If this is the case, speak with a tax professional to find out if you qualify.