2027 IRS Underpayment Interest Rate
The IRC §6621 underpayment rate by quarter — what is set, what is not, and when each quarter is published.
Not yet announced No 2027 figure exists yet, from anyone. (the publishing agency, retrieved 2026-09-19) The 2026 figures below are official and stand until the announcement.
| Item | 2026 | 2027 | Status |
|---|---|---|---|
| IRC §6621 underpayment interest rate, Q1 (Jan-Mar)Individual taxpayers | 7.00% | Not yet announced | Not yet announced |
| IRC §6621 underpayment interest rate, Q2 (Apr-Jun)Individual taxpayers | 6.00% | Not yet announced | Not yet announced |
| IRC §6621 underpayment interest rate, Q3 (Jul-Sep)Individual taxpayers | 7.00% | Not yet announced | Not yet announced |
| IRC §6621 underpayment interest rate, Q4 (Oct-Dec)Individual taxpayers | Not yet announced (last announced rate 7.00% carried forward) | Not yet announced | Not yet announced |
2026 figures as published by the publishing agency — source, retrieved 2026-09-19. Every figure on this page is read from a dataset at build time; none is typed into the page.
Underpayment penalties are a symptom — the cause is usually a withdrawal that moved your bracket. QuantCalc runs your whole retirement — withdrawals, taxes, Medicare surcharges — year by year, on 2026 and 2027 figures.
Run the free tax-aware simulation →How this figure is set
The federal short-term rate plus 3 points, re-determined every calendar quarter in a revenue ruling published roughly a month before the quarter starts. No 2027 quarter has been set (the publishing agency, retrieved 2026-09-19)
Common questions
Are the 2027 estimated-tax underpayment rate figures final?
There is no 2027 figure to be final about yet. The responsible agency has not published one. (the publishing agency, retrieved 2026-09-19)
What sets these numbers?
The 2026 figures are taken from the agency's own publication (the publishing agency, retrieved 2026-09-19).
What changed from 2026?
The table shows both years side by side so the change is readable directly. Where a row says unchanged, that is a statutory result, not an omission.
Related
Underpayment penalty calculator → 2027 tax brackets →
Every figure here with its status and source: JSON. QuantCalc is calculation software, not tax advice.