A plan is sponsored by Employer A. Due to reorganization of the employer, the legal entity known as Employer A cannot sponsor the Plan. The Plan Sponsor/Employer needs to be changed to Employer B with a new EIN. The same employees are covered under the Plan. The Sponsor/Employer address is unchanged as well. The name of the Sponsor/Employer and the EIN will change.

My presumption is that we just need to amend the Plan's definition of employer.

Am I missing anything? What about the subsequent 5500 filings which will be under a EIN different than the past? Will this raises questions from the DOL and if so, what do we do to address proactively?

Amending the plan sponsor is fine as long as it is acceptable to both the old and the new plan sponsor. You might want to have a joint resolution of the two plan sponsors indicating acceptability.

Once the plan sponsorship has been changed, you report the change on the 5500.