401(k) Plan Transferred to PEP

We have an audited plan that transferred to a PEP last year.  The assets transferred May 31, 2023, the PEP considered it a transfer of assets not a plan termination.  The auditors are doing a combined audit of 2022 and the for the short plan year period of 1/1/2023-5/31/2023 (when the assets transferred).  My question is... what is the due date of the Form 5500 for the short 2023 plan year? 

Thank you, 

The filing for the short plan year should be checked as the final filing for the plan, and the due date is the last day of the 7th month after the date of the transfer (which is the date plan assets went to 0).  That would put it due on 12/31/2023 unless it was extended 3/15/2024.

If the filing is late, the DFVCP is a bargain!

https://www.dol.gov/agencies/ebsa/employers-and-advisers/plan-administration-and-compliance/correction-programs/dfvcp