Sometimes there is work after a claimant's alleged onset date. The Work Activity Report - Employee addresses that issue.
Being disabled means you are not working. So it is entirely appropriate for Social Security to request the details for any work activity after the alleged onset date. After all, step 1 of Social Security's sequential evaluation is a consideration of your work activity. See 20 CFR 404.1520. One judge at the Boston ODAR requires every claimant to complete a Work Activity Report before a hearing.
When completing the Work Activity Report, be sure to have the correct dates of the beginning and end of your work. Be specific about your rate of pay and the hours worked. Be sure to say if the work ended due to your medical condition, or if the work ended because special conditions at work related to your medical condition that allowed you to work were removed.