You must generally appeal within 60 days from the date you received the denial letter. SSA will assume you received the denial letter within 5 days of the date shown on the letter unless you can show you did not receive it during the 5-day period. Thus, for all intents and purposes, you must submit your appeal no later than 65 days after the date on the denial letter.
However, if you are appealing a decision to stop your benefits (cessation cases), you must appeal within 10 days in order to continue your benefits pending the resolution of your appeal.
Also, if you are appealing an ALJ decision in a case that was previously remanded by a court, the deadline for an AC appeal is shortened to only 30 days.