Plan Year Change (after eoy)

Welfare Plan has reached 100 participants so it's time to file the very first 5500.

Apparently their existing plan document shows a 6/30 plan year end, but their policies are calendar year.

They'd like to change the plan year and create a short plan year for the last year (ie today is 4/20/22 and they would like a short plan year 7/1/21-12/31/21).

I think it's too late to retroactively (and easily) amend for that short plan year.

But curious of other's opinions in the following two scenarios, if it can be done:

1. 7/1/21 count < 100 so no 5500 required for a short 6-month plan year
2. 7/1/21 count > 100 so a 5500 would be required at 12/31/21 (not yet due)

I agree, it's too late now to do a 7/1/21 - 12/31/21 Short PYE.