I have a Mexican friend that has lived in Arizona for over forty years. He is retired from working for the state for 30 years and has a tax deferred retirement plan (I think 403-(b)). He wants his sister who lives in Mexico to be the beneficiary to the plan but he has been told by the administrator of the plan that the beneficiary needs to have a social security number. Of course Mexican citizens don't have SS numbers. What is he to do?