If I did not request to appeal a disability benefit denial upon recieving the denial letter, how long do I have to still appeal?

When Social Security makes a decision on your claim, you have 60 days to request an appeal.  Social Security assumes you got the letter five days from the date it was mailed.  Check the postmark on your letter from social security if it was more than five days from the date in your letter you can file a request for reconsideration and indicate on that form that you received the letter more than five days from the date of the letter to explain why it was late.

If you are more than 65 days late in requesting your appeal this still does not mean you must start your application over.  If you have a good reason for being late in filing the appeal such as a death in your family, being hospitalized or other good cause, you should still request the reconsideration and include in your request a statement or proof of why you failed to appeal within the time period allowed.

Social Security will reopen an application for any reason within the first 12 months of filing the application without requiring that you start the process from the beginning.  It would be a good idea to consider legal counsel if you are significantly late in appealing to get help with the process of requesting that your case be reopened and that you be allowed to appeal.