Plan retro effective to '21 for PS--5500?

Plan was created in August 2022 with a 1/1/21 effective date so they could do a PS contribution for '21.

Was there supposed to be a 5500 filed?  If so, how do you go about it?  Plan wasn't in existence until August, well after the extensions were due.

is there a special 5500 rule for plan that are retroactively adopted?

I think I may have found something:

 

Form 5500 Filing Requirement 

In August of 2021, the IRS issued an Employee Plan News bulletin that states that retirement plans that are retroactively adopted can skip the first year’s Form 5500 filing. Plans that are retroactively adopted become effective as of the last day of the first plan year, creating a one-day plan year that would normally require a Form 5500 filing. However, the IRS is allowing plan sponsors to file their first Form 5500 for the 2022 plan year, indicating on the filing by checking a box, that the plan was retroactively adopted.

Does anyone know where on the 5500 you indicate the plan was retroactively amended?

Box D - didn't paste in well, but see below

Form 5500-SF
Department of the Treasury
Internal Revenue Service
Department of Labor
Employee Benefits Security Administration
Pension Benefit Guaranty Corporation
Short Form Annual Return/Report of Small Employee
Benefit Plan
This form is required to be filed under sections 104 and 4065 of the Employee Retirement
Income Security Act of 1974 (ERISA), and sections 6057(b) and 6058(a) of the Internal
Revenue Code (the Code).
 Complete all entries in accordance with the instructions to the Form 5500-SF.
OMB Nos. 1210-0110
1210-0089
2021
This Form is Open to
Public Inspection
Part I Annual Report Identification Information
0BFor calendar plan year 2021 or fiscal plan year beginning and ending
A This return/report is for: X a single-employer plan X a multiple-employer plan (not multiemployer) (Filers checking this box must attach a
list of participating employer information in accordance with the form instructions.)
B This return/report is X the first return/report X the final return/report
X an amended return/report X a short plan year return/report (less than 12 months)
C Check box if filing under: X Form 5558 X automatic extension X DFVC program
X special extension (enter description)
D If this is a retroactively adopted plan permitted by SECURE Act section 201, check here. . . . . . . . . . . . . . . X

Visual aid

Yep thanks.  And Box E on the Form 5500.