20 C.F.R. § 404.705
Generally, you will be asked to give us by a certain date specific kinds of evidence or information to prove you are eligible for benefits. If we do not receive the evidence or information by that date, we may decide you are not eligible for benefits. If you are already receiving benefits, you may be asked to give us by a certain date information needed to decide whether you continue to be entitled to benefits or whether your benefits should be stopped or reduced. If you do not give us the requested information by the date given, we may decide that you are no longer entitled to benefits or that your benefits should be stopped or reduced. You should let us know if you are unable to give us the requested evidence within the specified time and explain why there will be a delay. If this delay is due to illness, failure to receive timely evidence you have asked for from another source, or a similar circumstance, you will be given additional time to give us the evidence.
20 C.F.R. §404.705