Form 5500 filed but not required - any notice to DOL necessary to stop filing?

Governmental entity mistakenly filing Form 5500-SFs for years.  Should we simply stop filing (and risk inquiry from DOL/IRS) or notify DOL/IRS that they will stop filing 5500s because they are not subject to ERISA?  

Having been through the ringer once to convince the DOL that a plan was not subject to filing because it was governmental, I would say prospectively notify them, maybe amend the last filing to include an attachment explains why they are no longer filing?  If they request a filing, and you are exempt, you may still have to submit a reason.  

I would agree with Gina to amend the last 5500 that was filed, update it to meet the requirements of a "final return," and attach a PDF statement explaining the plan is/was exempt from the 5500 requirement and why, and that the 5500s were filed in error.