Are HCE elective deferrals made to a multiemployer plan included in the ADR for purposes of testing the employers non-union plan ?

Example: HCE participates in non-union 401(k) and makes elective deferrals of $2,000. Same HCE becomes covered by a multiemployer plan (a bargained plan in which the employer participates but does not sponsor) during the year and remains employed by same employer. HCE makes elective deferrals of $10,000 to the multiemployer plan. participants.

When testing employer 401(k) Plan, is the HCE's ADR determined based on the $2,000 contributed to the employer sponsored plan or $12,000 contributed to both plans?

A strictly read of the (k) regulations indicate only the contributions made to the employer (as defined in 414(b), (c), (m) or (o)) plan should be included in ADR. I have heard the IRS has said contributions to both plans should be included.

Any real life experience ?