That's a great point to clarify. The IRS states: You may be able to claim your child as a dependent regardless of age if :
- He or she cannot engage in any substantial gainful activity because of a physical or mental condition.
- A doctor determines the condition has lasted or can be expected to last continuously for at least a year or can lead to death.
You mentioned the child is receiving SSI payments, which usually means that social security has deemed them disabled. I believe they typically do a re-evaluation at age 18 to see if benefits should continue. You may have some paperwork to that effect? Otherwise, does the autism diagnosis say anything about their ability to work? If your child is incapable of working full time at a minimum wage job, they would be considered disabled.
(If she works at a sheltered workshop that exists to try and teach work skills to disabled individuals, that work may be exempt for this purpose. And the income may not count for purposes of determining dependency.)
Here is a relevant IRS flyer: Living and Working with Disabilities
