29 C.F.R. § 4281.45

(a) Requirement of notices. For each insolvency year, the plan sponsor shall issue a notice of insolvency benefit level to the PBGC and to plan participants and beneficiaries in pay status or reasonably expected to enter pay status during the insolvency year. The notices shall be delivered in the manner and within the time prescribed in this section and shall contain the information described in § 4281.46.

(b) When delivered. The plan sponsor shall mail or otherwise deliver the notices of insolvency benefit level no later than 60 days before the beginning of the insolvency year. A plan sponsor that determines under § 4041A.25(b) that the plan is or may be insolvent for a plan year shall mail or otherwise deliver the notices of insolvency benefit level by the later of 60 days before the beginning of the insolvency year or 60 days after the date of the plan sponsor's determination under § 4041A.25(b).

(c) Method of delivery. The notices of insolvency benefit level shall be delivered by mail or by hand to the PBGC and to plan participants and beneficiaries in pay status or reasonably expected to enter pay status during the insolvency year.