"I've filed the 5500-EZ for my Solo401k for tax years 2021 (once it hit $250k) through 2025. I just noticed that the effective original date is 1/1/18, but I've been putting 1/1/19 on all the 5500-EZ forms from 2021 to 2025. Now, I'm considering opening up a Mega Backdoor Roth, and MySolo401k.net has to restate the Solo401k plan and needs the original effective date (I called E-Trade to ask and that's how I noticed the discrepancy). I've read horror stories on here about people amending their 5500-EZ forms that have been filed on time/yearly and being slapped (it seems automatically?) with late penalties of $150,000 per year ... [1] What do I do? Let sleeping dogs lie and continue putting the 1/1/19 date on the yearly 5500-EZ forms moving forward? If I put 1/1/18 on the 5500-EZ form for next year, will that trigger some kind of alert on the IRS' end with the associated $150,000 yearly penalties? [2] Do I need to amend every 5500-EZ from 2021 through 2025? [3] Does the plan restatement by Solo401k.net get sent to the IRS in any way or just to E-trade?"