Hi, you can claim a 28 year-old with special needs providing certain circumstance outlined below:
When your child reaches age 19, the rules change (for students, the rules change at age 24). You may still be able to deduct him as a dependent – provided that a few requirements are met. First, he must be permanently and totally disabled (if he is receiving Supplemental Security Income or Social Security Disability benefits he has been determined to be disabled).
Generally speaking, he must also live with you for at least half of the year (although there are a number of exceptions to that requirement), you must provide at least half of his support, and he cannot be claimed as a dependent on anyone else’s tax return.
These rules apply to your child, biological or adopted. They also apply to your stepchild, foster child, grandchild, brother, sister, niece, nephew or a descendent of any of those people.
There is actually another way your child can and certain other relatives may qualify as your dependent, and it does not require a finding of permanent and total disability. A “qualifying relative” can be a dependent even if he does not live with you (he has to be on a lengthy list of specific relatives, including children siblings, parents and many more), so long as you provide half of his support and he does not have income over $3,900 (in 2013 – this number will change each year).
The Internal Revenue Service has an excellent publication listing the finer details of claiming a child or other relative as a dependent. Look for Publication 501: Exemptions, Standard Deduction and Filing Information. It is updated annually.
Here is a link to Publication 501:
https://www.irs.gov/forms-pubs/about-publication-501
