Amendment Date for Merger

[Guest mwspaid]

One single employer plan is merged into another. Must the amendment for this merger be signed prior to the effective date of the merger? How about before the end of the plan year in which the merger takes place or retroactively during the following plan year. The 5310-A's will have been filed in a timely manner.

What if a board resolution regarding the merger is passed prior to merger. Does this allow for any type of retroactive amendment?