20 CFR § 404.909 - How to request reconsideration.
(2) At one of our offices, the Veterans Administration Regional Office in the Philippines, or an office of the Railroad Retirement Board if you have 10 or more years of service in the railroad industry.
(b) Extension of time to request a reconsideration. If you want a reconsideration of the initial determination but do not request one in time, you may ask us for more time to request a reconsideration. Your request for an extension of time must be in writing and must give the reasons why the request for reconsideration was not filed within the stated time period. If you show us that you had good cause for missing the deadline, we will extend the time period. To determine whether good cause exists, we use the standards explained in § 404.911.