Until What Age Can I Claim My Son on My Income Tax?

The IRS lets you claim two types of dependents on your taxes: qualifying children and qualifying relatives. Your son could be a qualifying child or a qualifying relative, depending on his age, income and other factors. To count as a qualifying child, your son must be under the age of 19 at the end of the year and have lived with you for more than half the year. Your child doesn't count as a qualifying child if he paid for more than half of his own support during the year or if he files a joint tax return.

The IRS extends the age limit for qualifying children for those in college. If your son is 23 and a full-time college student at the end of the calendar year, you can claim him on your income tax if he meets the other requirements for a qualified child. Temporary absences due to education and vacation don't count as time living away from you.

A "permanently and totally disabled" child can count as a qualifying child for tax purposes, regardless of age. A child is considered permanently and totally disabled if he cannot work due to a physical or mental condition and a doctor determines that the condition is expected to last at least a year or can lead to death.

You can claim an adult son of any age on your taxes if he meets the requirements for a “qualifying relative.” As of 2012, you have to provide more than half your son's support and his gross income cannot exceed $3,700. An individual doesn't count a qualifying relative if he counts as a qualifying child for you or any other taxpayer.