Adding SH to plan mid-year, any good resources

Are there any good resources on adding Safe Harbor to a plan mid-year (now)?

I was trying to wad through the EOB and ERISApedia, but I didn't find anything right away.  I figured someone here may know where the (current, updated) timing rules are, thus saving me some time and effort...

Thanks in advance...

Safe harbor match can't be added mid-year.

Safe harbor non-elective can be added up through November 30 (assuming calendar year plan) of the current year at 3%, or up through December 31 of the following year (i.e. 12/31/2027) at 4%.

That's what I thought.  Bur I also read something about if the plan has a discretionary match or something...

Where's a good place to see all these rules in one place?

The mid-year/retroactive safe harbor non-elective is only good for the ADP safe harbor. If you need the ACP safe harbor for a discretionary match, then you will have to wait until the next plan year.

Since you mentioned you have access to ERISApedia, chapter 14.12 has a great discussion on safe harbor plans. In particular there is a chart in 14.12.3.5 that I think will help you narrow it down. Remember that the notice has to be given before the beginning of the year, so if a notice is required then you can't make the change mid-year.