An S corporation letter and a personal K-1 are easy to mash into one math problem. They are two filings. Interest is a third thing sitting beside both.
Form 1120-S follows its own instruction. This page prints no dollar for it. Confirm the instruction for the year on the notice before you trust a figure someone remembered from a different year.
Form 1120, the C corporation return, uses the income tax failure to file math, including a minimum table. This page does not quote that table. The dollar lives on the IRS page with the other figures that move.
Interest uses the rate for the quarter, and it compounds every day. A balance that is still open when a new quarter starts picks up the new rate from there. The rate is not printed on this page, because it changes. The IRS publishes the quarter.
Source. Quarterly interest rates are published by the IRS. Read 29 September 2026 at https://www.irs.gov/newsroom/interest-rates
Source. Failure to file is five percent of the unpaid tax per month or part of a month, capped at twenty five percent. The base is tax required to be shown, minus timely payments and refundable credits. After sixty days a minimum table can apply, and the dollar in that table is on the page. Read 29 September 2026 at https://www.irs.gov/payments/failure-to-file-penalty
Working out which charge a letter means, and keeping the books that stop the next one, is what happens here. A hearing, an appeal or any filing made on your behalf as your representative belongs with a firm that does that work, and no CPA license sits at this desk either, so signed reports on your statements go elsewhere as well. You'll hear both of those early rather than late. The longer drawing of the limit lives on the disclosures page.
A balance can pick up a new rate at the quarter even when you have already named the filing charge. Keeping them apart is the whole trick.
Send the form number. We will say whether you are looking at an S corporation instruction, a C corporation minimum, or interest, and we will not invent the dollar.
Form 1120 and Form 1120-S should not share a sentence on your note. Pick one.
You will be talking to the Steven Palmieri practice.