To follow the statute, a plan’s administrator (if it uses the safe-harbor explanation) should have rewritten its § 402(f) notice as soon as the preceding safe-harbor explanation no longer met the commands of § 402(f)(1)(A)-(E).
Whatever reliance Notice 2018-74 afforded, one gets no reliance to the extent that an explanation is no longer accurate because of a law change after September 18, 2018. (A caution of that kind has been in successive IRS Notices with revised safe-harbor explanations.)
Yet many service providers wait for the IRS’s release of a revised safe-harbor explanation.
Some businesspeople imagine the Internal Revenue Service might be reluctant to assess a penalty against an administrator if it delivered an otherwise proper notice grounded on the preceding safe-harbor explanation and the only defect is incorrect or incomplete content while waiting for the IRS’s revised safe-harbor explanation.
Likewise, some administrators estimate (whether expressly or impliedly) a modest exposure to liability for a distributee’s reliance on incomplete, incorrect, or misleading information.
For an administrator or service provider that waits for the IRS’s revision of a safe-harbor explanation, it seems wise to implement a new version promptly after the IRS publishes it.