20 CFR §404.908

1. (a)Who may request a reconsideration. If you are dissatisfied with the initial determination, you may request that we reconsider it. In addition, a person who shows in writing that his or her rights may be adversely affected by the initial determination may request a reconsideration.
2. (b)Who are parties to a reconsideration. After a request for the reconsideration, you and any person who shows in writing that his or her rights are adversely affected by the initial determination will be parties to the reconsideration.