29 CFR §4043.64

1. (a)Reportable event. Advance notice is required for a distribution by a member of a plan's controlled group, as described in § 4043.31(a).
2. (b)Waiver—de minimis 5-percent segment. Notice under this section is waived if the person making the distribution is a de minimis 5-percent segment of the plan's controlled group for the most recent fiscal year(s) ending on or before the effective date of the reportable event.