I just looked this up on the US Code here on Benefits Link. Here is what it says under 6057(e):
(e) Individual statement to participant
Each plan administrator required to file a registration statement
under subsection (a) shall, before the expiration of the time prescribed
for the filing of such registration statement, also furnish to each
participant described in subsection (a)(2)© an individual statement
setting forth the information with respect to such participant required
to be contained in such registration statement. Such statement shall
also include a notice to the participant of any benefits which are
forfeitable if the participant dies before a certain date.
It looks to me to be the just annual participant statements. If you want to read the whole section, go to
http://benefitslink.com/buzz/new.shtml and click on the Internal Revenue Code over to the left. Then click on the first choice..."code sections relative to employee benefits" or something like that. Once there you can scroll down to 6057. Hope this helps.
Sorry for the two edits, I go to everything automatically on my computer, so I wasn't being careful about the references. These should be correct now!