If a plan defines 1st year eligibility as something like "Anyone in employment on xx/yy/zz enters immediately. Anyone employed after that date enters on the next entry date after completing 21/1", no one is excludable for purposes of 410b/401a4 for the first plan year. What if 21/1 also applies to to the "Anyone... on xx/yy/zz"? Are those employed after the magic date now excludable? In other words, are the entry dates relevant? Or do I now have an amendment that may discriminate in favor of HCEs?

is this what you are looking for? (I added this one to be in the supplement this year for the book)

If a new plan provides for immediate entry for those employed on a certain date, and a waiting period for those hired after that date, might this be considered a discriminatory amendment?

The very same question was asked at the 1999 ASPPA Annual Conference IRS Q and A question forum.

IRS Response: This provision is often seen in standardized prototypes which are supposed to be nondiscriminatory by design. I do not think present and future eligibility would have been approved in standardized prototype plans if this were not acceptable.
We do not see this eligibility provision as a discriminatory amendment under the -5 rules.
It should be remembered that IRS responses at such conferences represent an unofficial view of the government participant at the time of the discussion, and not necessarily represent agency policy.

My understanding was that the IRS stopped approving that design in standardized prototypes after they were made aware of that issue.

Merlin:
is the document in question new, and has it an approval letter?
If so, I am not sure how a standardized plan can fail.

Katherine may be right that this is an issue the IRS is not allowing any more, but I haven't seen anything on it, so I couldn't say for sure.

Tom, the document doesn't exist yet. At this point the question is purely hypothetical.