Traditional large 401(k) plan (not safe harbor) with 9/30 year end - original effective date 1987.
Volume submitter adoption agreement defines compensation as W-2 wages and does not exclude bonuses.
This is a new client for us; our firm is doing the audit for the 9/30/2019 plan year end, taking it over from the prior auditor (who recommended us).
We see that various bonuses were paid to employees for performance, safety, etc. at year-end. However, the plan sponsor did not calculated or withheld deferrals from bonuses. As far as we can tell, they have never withheld deferrals from bonuses, and did not realize they were supposed to do so. They are restating the plan to give employees the option to elect out of deferring from future bonuses.
The question is: what to do about the past? The plan sponsor has been operating in a manner that would have been permissible under law but not in conformity with their plan document. Does their consistency for the past 20+ years show that they never intended to include bonuses in the definition of 401(k) compensation? Will that consistency protect them from penalties and sanctions?
If not, what is the fix for this? How far back would they need to go to "make it right"? Do they need to include all plan participants who have deferred or can they elect to exclude the HCEs from the fix?
Thanks!