Lost vs Non-Responsive Participant

[ERISA1]

Let's say an employer mails an automatic rollover notice by first class mail to a participant's last known address. The notice is not returned. Can the employer safely assume the employee is non-responsive, and therefore, rollover the benefit to an IRA? Or, should the employer take additional steps ("due dilligence") to prove that the participant received the notice?

If additional steps must be taken to prove that a participant is NOT lost, what would you suggest? Certified Mail would provide proof only if you can confirm that the Participant signed the receipt. What if the Participant refuses to sign the receipt; how do you document that? Should you use a locator service to confirm you wrote to the correct address?

I would suggest that due dilligence follow-up is required only if there evidence that the Participant is lost. That is, only if a first class letter is returned.

Thanks