Form 5330

[Chippy]

Plan has a late contribution deposit in 11/2015. Company realized it and deposited the contribution three weeks late. Late deposit was found during large plan audit.

Lost earning were calculated and were deposited to the plan in 7/2016.

I'm preparing the 5330. Would the filer tax year be 2015, they have a calendar year. and if so, then the form is late since a 5558 was not filed,

Or is the tax year 2016 since that is when the lost earnings were deposited?

I've been reading and reading, and it seems like it should be reported for 2015, but doesn't seem fair since it wasn't discovered till it was found in the audit. Employer didn't realize it had to be reported as late.

And if the 5330 is prepared for 2015, I have to prepare another 5330 for 2016 since that is the year it was corrected. Is there another excise tax due for 2016? if so, what is that based on?