As a 401(k) plan sponsor, you need to make sure that all your plan providers understand any ownership interests in other companies that you may have and make a determination whether those interests constitute a controlled group or affiliated service group.
The problem is that if you don’t do the analysis, you may run afoul of the qualification rules because controlled and affiliated service rules treat the members of these groups as a single employer for most purposes. So if your company is a part of these groups and you do nothing, you may have a huge coverage problem if the other companies don’t have a similar retirement plan. Even if they do have similar plans, there could be discrimination testing problems since all companies need to be tested as one.
So when you get the census information, make sure you answer correctly when it comes to the questionnaire asking you about other ownership interests.