Hi Mike9241. Thanks for the quick reply! I've paid small amounts of penalty interest many times before, using TT, and never had this issue come up. It is unfortunate that TT does not consistently do the penalty calculation accurately (anymore?) - that makes it of marginal value. What other calculations does TT not do accurately? And I didn't enter dates - as far as I know, the TT penalty calculation assumes the underpayment is spread evenly throughout the year. I also filed the return and paid on time. And, yes, there is a phone number on the notice. I called it before I asked about this issue here. Of course, the number is of no value because a recording comes on that says they cannot help due to large call volume and just hangs up.
