"I forgot it and he is thinking regarding social security benefit since he is 62"

Sounds to me like you don't have a very honest client.  It sounds like his memory is getting wishy washy either because of age or his memory is trying to balance out taxes with long term benefits.  Personally, I would tell this client to have a nice life.  Life is too short for tax preparers when they are stuck dealing with clients that like to play games with their taxes.