What information must you include in determination letter request re plan-to-plan transfer

[Guest BL333]

We have a client who acquired the stock of another company a few years back and continued to have employees of that previous company continue to participate in the previous company's multiple employer plan. Our client has now done a plan-to-plan transfer from the multiple employer plan to its own 401(k) plan. When we submit for a determination letter request for our 401(k) plan, how much information do we need to include on the previous multiple employer plan and the plan-to-plan transfer itself? I know that when we merge a plan, we include all of the amendments, previous determination letter, etc. for the merged plan prior to the merger, but I cannot seem to find guidance saying whether this level of detail is also required upon a plan-to-plan transfer. I am asking because the multiple employer plan has been quite difficult to deal with and seems unwilling (without a fight) to provide us with all the information we would need. If anyone can point me to any guidance on this issue, I would greatly appreciate it!

Many thanks!