Solo 401k 5500-EZ filed through IRS relief program still subject to DOL penalties?

I need to file two 5500-ez via the IRS relief program dating back 7 & 8  years when my solo/individual 401k exceeded $250k (I was ignorant of the requirement to do this). The $500 penalty per submission is a bargain compared to the alternative.

What I don't understand is why the Department of Labor DFVC program doesn't also cover solo 401k's 5500-ez submissions  - won't the paper submission of the delinquent 5500-ez via the IRS relief program almost certainly trigger an insanely high penalty dating back 7/8 years from the Department of Labor as well?

No. There is a requirement under Title I of ERISA to file the 5500, but that only applies to plans which are subject to Title I. Plans which cover only the 100% owner of a business, or partners in a partnership, are exempt from Title I. The reason the 5500-EZ exists is for those plans to provide a report to the IRS, since the DOL reporting requirements don't apply.

For the most part, a plan which can file 5500-EZ is the same thing as a plan which is exempt from Title I. That line has become a little blurred recently, but there is coordination between the IRS and the DOL here. A plan administrator is only required to file either the 5500-EZ or the 5500(-SF) for any given year.

Thanks - appreciate the clarification.