Penalties & interest stack

See how failure-to-file, failure-to-pay, and interest pile up over months

Tax year 2025 New D2 · cross-cutting
What this does

Slide unpaid tax and months late to watch three additions grow: failure to file (FTF), failure to pay (FTP), and interest. Clean 2D charts show which piece bites first and when FTF dominates.

Teaching model of civil penalty rates — not a live IRS calculator. Study tool only.

Rule · rates FTF = 5%/month of unpaid tax (cap 25%). FTP = 0.5%/month (cap 25%). When the return is not filed, FTF is reduced by FTP for the same months. Interest runs separately on underpayments.

Your scenario

Unpaid tax, how late you are, and whether the return was filed.

Return status

Watch out · assumptions: Interest ≈ unpaid tax × annual rate × months/12 (simple teaching approximation; real IRS interest compounds daily). Minimum FTF dollar floors on small balances are not modeled.

Key totals

One glance: what you owe beyond the tax itself.

FTF penalty
—
5%/mo · max 25%
FTP penalty
—
0.5%/mo · max 25%
Interest (approx.)
—
Teaching rate
Running total — tax + all additions
—

—

FTF FTP Interest Original tax

Stacked growth over months

Watch each layer accumulate as months tick by for your unpaid tax amount.

Additions by month · stacked area (2D)
Watch out FTF hits its 25% cap at just 5 months of non-filing. FTP needs 50 months to hit the same 25% cap — filing late hurts much faster than paying late alone.

Compare pieces at this month

Side-by-side bars: FTF vs FTP vs interest for a few unpaid-tax levels at your current months late.

Grouped bars · FTF / FTP / interest by unpaid tax
Donut · composition of additions at current inputs
Exam trap: FTF (5%) is much steeper than FTP (0.5%) — filing late hurts faster than paying late alone. When both apply, FTF is reduced by FTP for the same months (you don’t stack full 5% + 0.5% independently). Minimum FTF dollar floors can apply on small balances (not modeled here). Interest runs on underpayments separately from penalties.
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Study tool only — not official IRS software. Penalty percentages are general IRC §6651 teaching rates; interest rate is a labeled assumption, not a live IRS underpayment rate feed. Confirm against current IRS pubs before the exam.