A Qualifying Child dependent that is disabled by the IRS rules for disabled can be claimed at any age as long as the other Qualifying Child rules are met. A qualifying Child is eligible for the EIC.
Per IRS Pub 17
Permanently and totally disabled.
Your child is permanently and totally disabled if both of the following apply.
He or she can’t 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.
---Tests To Be a Qualifying Child---
(Must pass ALL of these tests)
NOTE: If a child passes all of these tests he must say “yes” on his/her own tax return (if he/she files one) that another taxpayer CAN claim him/her as a dependent even if they DO NOT claim him/her)
1. The child must be your son, daughter, stepchild, foster child, brother, sister, half brother, half sister, stepbrother,stepsister, or a descendant of any of them.
2. The child must be (a) under age 19 at the end of 2016, (b) under age 24 at the end of 2016 and a full-time student* for any part of 5 months of 2016, or (c) any age if permanently and totally disabled and must be younger than you (or your spouse if filing jointly).
3. The child must have lived with you for more than half of the year (There are exceptions for temporary absences such as school, illness, business, vacation, military service).
4. The child must not have provided more than half of his or her own support for the year.
5. If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child.
6. The child is not filing a joint return.
7. The child must be a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico
*A full-time student is a student who is enrolled for the number of hours or courses the school considers to be full-time attendance during some part of each of any 5 calendar months of the year.
See IRS Publication 17 for more information.