Multiple employer plan

[Guest cosmo01]

We have a situation where we have adopted a prototype 401(k) plan. We are in the process of establishing a new corporation that will NOT be within our controlled group of corporation, but we want to enable this corporation to participate in the 401(k) plan. We plan on converting the current prototype 401(k) plan into a multiple employer plan to permit the unrelated corporation to adopt it. What must we do to accomplish this? Is there any guidance that might be helpful?

Thank you