29 C.F.R. § 4043.34 – Loan default.

(a) Reportable event. A reportable event occurs for a plan when, with respect to a loan with an outstanding balance of $10 million or more to a member of the plan's controlled group—
1. (1) There is an acceleration of payment or a default under the loan agreement, or
2. (2) The lender waives or agrees to an amendment of any covenant in the loan agreement the effect of which is to cure or avoid a breach that would trigger a default.
(b) Waivers—(1) De minimis 10-percent segment. Notice under this section is waived if the debtor is not a contributing sponsor of the plan and represents a de minimis 10-percent segment of the plan's controlled group for the most recent fiscal year(s) ending on or before the date the reportable event occurs.
(2) Foreign entity. Notice under this section is waived if the debtor is a foreign entity other than a foreign parent.