Split 401k to avoid audit retro to first day

Is it permissible to spin-off a portion of a safe harbor 401k plan to an identical safe harbor 401k plan for a calendar plan year after January 1st of the current year with an effective date of January 1st to avoid a plan audit for the 2018 plan year? Safe harbor mid-year amendment issues?

No.  You could do it effective January 1, 2019.  Seems as if you're approach is a few months late.

Good Luck!

one reason I can think of not allowing this:

the notice MUST

1.401(k)-3(d)(2)(C) the plan to which the safe harbor contribution will be made (if different from the plan containing the cash or deferred arrangement)

therefore, you can't have given a notice in Dec 2017 saying deferrals and safe harbor will be made to Plan A and now at this late date say

"oh by the way, we were just kidding, if you are so and so, your deferrals and safe harbor will be made to plan B retroactive to 1/1"

Thanks for the replies. Confirming what I suspected. Making sure there wasn't some loophole.