Individual was hired and worked for a company for a number of years. During this time person did deferrals and received employer contribution under qualified 401(k) Plan. Person is 100% vested. (We are talking about a long emploment.)

Problem becomes known after person terminates emploment and "disappears". Turns out that person's documentation (social security card, birth certificate...) were fraudulent!

How does this become know? Social Security Administration contacts employer to alert the firm that it appears that person was using social security number of dead person! Beyond all other related problems, what should be done with monies held for this person under the 401(k) Plan?

The trail to prior threads starts here.

Wow! That is a long and varied trail. Having read most of it (my eyes started to bug out), I surmise that the employer should first employ the "IRS Locator" or "SSA Locator" service to begin a paper trail of showing a good faith attempt to locate the person. Then, when the person is not found, handle as you would whenever a person can't be found. (They have already taken several steps to find the person, but to no avail. We also know SSA is already looking for this person, and has not yet found.) If, however, the person is found, get legal counsel before doing anything. Sound reasonable?

Since the person used a false SS number to get hired it is highly unlikely that he will be located through IRS or SS which will use same SS number to locate ee (holder of ss# is dead). In the event that he cannot be located the benefits can be forfeited (if plan permits or can be amended) and used as future contributions.

Not only is that person dead, but dead in another country! While this is not important I thought I would just add that fact.