Plan Mergers/Controlled Group

What are the requirements and timelines for participant notification that they're plan is being merged/adopted by another common owner in a controlled group?  Any input would be appreciated.

From a statutory perspective, you'll want to ask about blackout dates as there will likely be a need for SOX Blackout notice at least 30 days in advance. Also consider the investment lineup in each plan. Will investments map to the same vehicles, or will these be changing? If changing, will there be a new default investment possibly triggering a QDIA notice. I usually see a 60-90 day lead time for informational notices to participants. These may not be required but certainly lead to a better participant experience, especially if there are significant changes. If this is a 401k plan, will deferral and/or investment allocation elections transfer or will new elections be required? Plan design will drive a lot of what an employer will want to communicate.