What to do if I believe I owe a penalty but the IRS has not notified me I do?

[JacobMecina]

For context, I made an excess contribution of $6500 to my Roth IRA in 2023 and didn't realize until 2025. Most things are now resolved (I mailed an amended 2023 return and paid the 6% = $390 penalty, I included another $390 penalty in my 2024 return, and I remedied the contribution so it shouldn't cause anymore issues in the future), but I think I still owe penalties + interest on the $390 I should have paid in Apr 2023 but didn't until Feb 2025.

I believe this case constitutes as both a Failure to file (since I didn't submit Form 5329 due in Apr 2023 until Feb 2025) and a Failure to pay (since I didn't pay the $390 due in Apr 2023 until Feb 2025). Notably, failure to file interest starts accruing the day that the original form was due, not the day the IRS notifies me (and interest continues to accrue until all outstanding payments, penalties, and interest are paid off).

However, I've received no notification from the IRS that I owe any penalty, even though I'm pretty sure I do. Assuming that I do owe a penalty and that the IRS is just slow in notifying me, that means that while I wait to receive a notice, the interest on the failure to file penalty is continuing to accrue. Thus, I'd much rather pay earlier to lessen the effects of interest, but without an official notice, I don't know exactly how much I need to pay. I could use something like a tax penalty/interest calculator, but it's not an official source like an IRS notice would be, nor am I sure if the amount is technically correct (the website even says the payoff amount is estimated).

So I'm not sure what I should do. Should I:

1. Try to alert the IRS somehow that I owe the penalty so they can send me the "bill" sooner rather than later and I can pay exactly the amount I need?
2. Try to calculate how much I owe myself and pay the IRS with the risk I miscalculate?
3. Wait for the IRS to send me a notice (if they send one at all) before paying, where the extra time spent waiting means the amount I owe grows higher due to interest (this last one also feels a bit like tax evasion, since I know I owe the IRS money but am not actively doing things to remedy this).

[JotikaT2]

Since you have taken all the steps possible to ensure you are now compliant and have paid all taxes due, you may be able to contact the IRS directly to either confirm the amount of any penalties or interest you may owe, or to ask that any outstanding penalties be abated using Form 843, Claim for Refund and Request for Abatement.

Please see Penalty relief from the IRS for more details.