2027 IRS Underpayment Interest Rate
Updated · 2026 figures official · 2027 figures not yet announced
The IRC §6621 underpayment rate by quarter — what is set, what is not, and when each quarter is published.
The 2027 figures have not been announced yet. For 2026, the IRC §6621 underpayment interest rate, Q1 (Individual taxpayers) is 7.00%; IRC §6621 underpayment interest rate, Q2 (Individual taxpayers) is 6.00%; IRC §6621 underpayment interest rate, Q3 (Individual taxpayers) is 7.00%, with 1 further figure in the table below.
Not yet announced No 2027 figure exists yet, from anyone. (IRS Rev. Rul. 2025-22, 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 | 7.00% | Not yet announced | Not yet announced |
2026 figures as published by IRS Rev. Rul. 2025-22 — 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 (IRS Rev. Rul. 2025-22, 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. (IRS Rev. Rul. 2025-22, retrieved 2026-09-19)
What sets these numbers?
The 2026 figures are taken from the agency's own publication (IRS Rev. Rul. 2025-22, 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 → 2026 estimated tax calculator: what to pay by January 15 → 2027 tax brackets →
Every figure here with its status and source: JSON. QuantCalc is calculation software, not tax advice.