We represent a plan that has a few participants, some with significant account balances, who cannot be located. These participants are approaching their required beginning dates and the administrator is getting nervous. He would like to distribute these accounts in accordance with the EBSA guidelines for terminating dc plans with missing pparticipants. Is this possible/advisable? It seems that the EBSA gidelines only apply to terminating plans. If we don't distribute these accounts, is the plan in any potentially difficulty under the RMD requirements? Can we just hold these accounts indefinitely? Any thoughts would be appreciated.

One step is to try the IRS Letter Forwarding Program.

http://www.irs.gov/retirement/article/0,,id=110139,00.html

I am just trying it for the first time myself so I can't vouch for its effectiveness, but it is one element of a "diligent search."