Can I claim my 22 year old son with asperger's if he already filed his taxes? he is my dependent and cant hold down a full time job or live independently?

[macuser_22]

Probably not if he had enough income to file a tax return and is not a full-time student.  If he is a full-time student then he might qualify to be your "Qualifying Child" dependent.

He would not qualify as a "Qualifying Relative" dependent if over $4,050 of taxable income.

He probably does not fit the IRS requirement for "disabled" if he can earn enough income to file a tax return.

The IRS defines disabled this way:

Permanent and total disability.

You have a permanent and total disability if you can't engage in any substantial gainful activity because of your physical or mental condition. A qualified physician must certify that the condition has lasted or can be expected to last continuously for 12 months or more, or that the condition can be expected to result in death.
Substantial gainful activity.

Substantial gainful activity is the performance of significant duties over a reasonable period of time while working for pay or profit, or in work generally done for pay or profit. Full-time work (or part-time work done at your employer's convenience) in a competitive work situation for at least the minimum wage conclusively shows that you are able to engage in substantial gainful activity.

Claiming disabled has no tax benefit unless child care was necessary so that you could work that normally cuts off after age 12, but is allowed if the care is necessary for an older disabled child.

It also allows claiming a Qualified Child as a dependent beyond the age of 18 and would do nothing for a younger child.

[DoninGA]

Assuming that he is not a full time student, if he had gross income of $4,200 or more in 2019 then no one can claim him as a dependent.

If his income was less, then you may be able to claim him under the Qualifying Relative rules if he meets all the requirements since he older than 18 and not a full time student.

To be a Qualifying Relative -

1. The person cannot be your qualifying child or the qualifying child of any other taxpayer. A child is not the qualifying child of any other taxpayer if the child's parent (or any other person for whom the child is defined as a qualifying child) is not required to file an income tax return or files an income tax return only to get a refund on income tax withheld.
2. The person either (a) must be related to you or (b) must live with you all year as a member of your household.
3. The person's gross income for the year must be less than $4,200 (social security does not count) in 2019
4. You must provide more than half of the person's total support for the year.
5. The person must be a U.S. citizen or a U.S., Canada, or Mexico resident for some part of the year.
6. The person must not file a joint return with their spouse.

He would have to file an amended 2019 tax return to change his dependency, assuming that he did not indicate on his tax return that he was a dependent.

See this TurboTax support FAQ for amending a 2019 tax return - https://ttlc.intuit.com/community/tax-topics/help/how-do-i-amend-a-2019-return-in-turbotax/01/123845...

You will have to print and mail your tax return claiming him as your dependent.  If you are owed a federal tax refund, the IRS will pay the refund.

See this TurboTax support FAQ for printing a tax return for mailing - https://ttlc.intuit.com/community/printing/help/how-do-i-print-and-mail-my-return-in-turbotax-online...

The other possibility is that you can claim him under the Qualifying Child rules where his income is not a factor.  You would have to indicate that he is Permanently and Totally Disabled.  He would still have to amend his 2019 tax return to change his dependency status.

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.

To be a Qualifying Child -

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 the year, (b) under age 24 at the end of the year and a full-time student or (c) any age and permanently and totally disabled.
3. The child must have lived with you for more than half of the year. Temporary absences while away at college are considered living with you.
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 must be a U.S. citizen or U.S., Canada or Mexico resident for some portion of the year.
7. The child must be younger than you unless disabled.