Can you provide some details on the matter that was involved in CP 2501.....and your reply?
From your details...it seems like a case of underreported income. What the IRS will do is assess tax on the unreported income, charge additional tax and also levy penalty and interest. Once you get that notice from the IRS, I would suggest you to make the payment asap and also to discuss with the IRS and try to get the penalty waived by explaining the entire situation.
They may not waive the penalty on the ground that you should have tried to get the income details from the trust or from the IRS when you found that the papers were lost but it is definitely worth a try.
Let me know if you have any question.
Please note: This advice is provided with the understanding that all the relevant facts have been provided by you. Any change in facts might affect the advice given and hence may not be relied on in such cases.
There is a penalty for not paying the taxes that you owed and also penalty for underpayment of the estimated taxes. This may apply in your case since some of your income was not reported and hence tax on that part of income was not paid.