Gather the documents verifying your mental illness. The SSA needs proof of your diagnosed condition. You'll need a statement from your doctor or psychiatrist, psychiatric records or test results and a list of any medications you are on.
Gather the documents to verify your income or previous income. You'll need your W-2 or federal tax return from the previous year, and a statement of any earnings for the current year.
Determine how you want to apply. The SSA offers an online application, as well as a phone application. You can also visit your nearby Social Security office to apply in person.
Complete the application (Form SSA-368-BK). Make sure you fill out everything carefully. Don't leave blank spaces on your application.
Submit the application online. If you are applying over the telephone, this is done for you. If you are applying in person, simply turn in the completed application to the representative.