Enter the balance and three dates; get the statutory math — both penalties, the overlap credit, interest, and the share an abatement request could remove. Runs entirely in your browser.
Statutory math, computed locally in your browser — nothing is sent anywhere. Your IRS transcript is always the controlling number; this shows you what the assessment should look like and what abatement is worth.
The penalty math will appear here.
The estimate above runs the statutory structure: 5%/month filing penalty netted against the 0.5%/month payment penalty in overlap months (so the pair totals 5%), independent 25% caps on each, the installment-agreement half-rate where it applies, and daily-compounded interest at your entered rate. What it deliberately doesn't guess: your exact assessment dates and quarterly rate changes — which is why the transcript always wins arguments, and why the useful output here is the abatable share.
Every notice page explains the deadline and drafts the response letter free — find yours.
Look up your IRS notice →Three meters run at once: failure to file (5%/month to 25%, reduced by the failure-to-pay rate in overlapping months), failure to pay (0.5%/month to 25% — 0.25% on a payment plan), and interest (federal short-term rate + 3 points, compounded daily, reset quarterly) on the tax and, from the notice date, on assessed penalties.
Rounding conventions, the exact assessment dates, rate changes mid-period, the 60-day minimum penalty, and interest-on-penalty accruals all shift the figure. The transcript is the authoritative ledger — this calculator shows the structure so you can sanity-check it and size an abatement request.
The two penalty lines — through first-time abatement or reasonable cause — plus the interest that accrued on whatever penalty is removed. Interest on the tax itself is effectively permanent until paid; only an IRS error or delay abates it.
The IRS underpayment rate for individuals: federal short-term rate plus 3, announced quarterly (recent years have run 7–8%). Enter the rate for your period — or run it at two rates to bracket the answer.