Notice for Missed Deferral Opportunity

I've been finding contradictory info about whether or not such a notice is needed in my situation.  An employee's date of entry was 1/1/26, but he was not informed that he could start deferring at that time.  The employee has yet to complain to the employer about this - it was the employer who caught this error.  The employee will be permitted to begin deferring with the first payroll period ending after 4/1/26.  This should suffice for reducing the QNEC for the MDO to 0%.  The plan does not have any autoenrollment features.  Some sources say an MDO notice is still needed, some say it is not.  I'm leaning more to the 'not needed' side, especially since the employee has not brought up the discrepancy - is this the way to go?  Any help is appreciated.

To allow a $0 correction, then the employer should provide the 45-day special notice after the correction begins. If the employer wants to give the 50% QNEC as part of the correction, then no notice is necessary.

Look at Rev Proc 2021-30.

Just to be sure, any reduced correction requires a notice (0% or 25%)

That's actually not true, there is no notice required.  There are tw rules relating to 3 months or less. You guys are referring to the newer 3 month rule, but there is an old ancient 3 month rule called the "Brief Exclusion" rule that has been on the books since the early days of EPCRS (well I just know it predates all the 45 day notice stuff).  This one is found in Appendix B of EPCRS and says there is no MDO correction if the participant can contribute for the LAST 9 MONHTS of the plan year. So the failure has to be limited to the first 3 months of the plan year.  Still of course 100% of missed match is due.

Appendix B, Section 2.02, in this (F).  I could not figure out the precise citation because of how the formatting shows up.  But this text is there.

(F) Special Rule for Brief Exclusion from Elective Deferrals and After-Tax Employee Contributions. An Plan Sponsor is not required to make a corrective contribution with respect to elective deferrals (including designated Roth contributions) or after-tax employee contributions, as provided in sections 2.02(1)(a)(ii)(B) and (C), but is required to make a corrective contribution with respect to any matching contributions, as provided in section 2.02(1)(a)(ii)(D), for an employee for a plan year if the employee has been provided the opportunity to make elective deferrals or after-tax employee contributions under the plan for a period of at least the last 9 months in that plan year and during that period the employee had the opportunity to make elective deferrals or after-tax employee contributions in an amount not less than the maximum amount that would have been permitted if no failure had occurred. (See Examples 6 and 7.