You would add your son as your dependent on your taxes and you would check off the box that asks if he has a disability and they ask you questions if you pay for most of the household expenses and you would check off yes and also that he lived with you for the year that's all you have to do
Yes, you can claim an adult that's disabled on your tax return. Since he's your son, he could be treated as a qualifying child and you may also be eligble for Earned Income Credit for him. The following tests have to be met to claim your adult son as a qualifying child:
1. Relationship: met (he's your son)
2. Age: met (since he's disabled, there's no age limit)
3. Residence: if he's lived with you more than 6 months, this is met
4. Support: if he didn't pay more than half of his own support, this is met
If all of the above tests are met, you can claim your son as a dependent and for Earned Income Credit. Additionally, if you paid someone to care for him while you were working, you may qualify for the Child and Dependent Care Credit.