{
  "title": "2027 IRS Underpayment Interest Rate",
  "canonical": "https://quantcalc.app/underpayment-rate-2027/",
  "base_year": 2026,
  "target_year": 2027,
  "license": "CC-BY-4.0",
  "date_modified": "2026-09-19",
  "projection_factor": 0.030600000000000002,
  "projection_factor_label": "+3.06%",
  "status_vocabulary": {
    "OFFICIAL": "Published by the responsible agency for 2027.",
    "PROJECTED": "A QuantCalc projection under the statutory indexing formula; the agency has not published a 2027 figure.",
    "UNCHANGED": "2027 equals 2026 as a matter of regulation or statute — nothing is being forecast.",
    "NOT YET ANNOUNCED": "No 2027 figure exists yet, from anyone, and this dataset does not invent one."
  },
  "family": {
    "statute": null,
    "index": null,
    "rounding": null,
    "source": "No 2027 quarterly rate published as of 2026-08-12",
    "sourceLabel": "the publishing agency",
    "method": "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",
    "notProjected": null,
    "title": "Estimated-tax underpayment rate"
  },
  "rows": [
    {
      "label": "IRC §6621 underpayment interest rate, Q1 (Jan-Mar)",
      "scope": "Individual taxpayers",
      "v26": "7.00%",
      "v27": "Not yet announced",
      "status": "NOT YET ANNOUNCED",
      "method": "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",
      "src26": "IRS Rev. Rul. 2025-22",
      "src27": "No 2027 quarterly rate published as of 2026-08-12",
      "numeric": {
        "v26": 7,
        "v27": ""
      }
    },
    {
      "label": "IRC §6621 underpayment interest rate, Q2 (Apr-Jun)",
      "scope": "Individual taxpayers",
      "v26": "6.00%",
      "v27": "Not yet announced",
      "status": "NOT YET ANNOUNCED",
      "method": "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",
      "src26": "IRS Rev. Rul. 2026-5",
      "src27": "No 2027 quarterly rate published as of 2026-08-12",
      "numeric": {
        "v26": 6,
        "v27": ""
      }
    },
    {
      "label": "IRC §6621 underpayment interest rate, Q3 (Jul-Sep)",
      "scope": "Individual taxpayers",
      "v26": "7.00%",
      "v27": "Not yet announced",
      "status": "NOT YET ANNOUNCED",
      "method": "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",
      "src26": "IRS Rev. Rul. 2026-10",
      "src27": "No 2027 quarterly rate published as of 2026-08-12",
      "numeric": {
        "v26": 7,
        "v27": ""
      }
    },
    {
      "label": "IRC §6621 underpayment interest rate, Q4 (Oct-Dec)",
      "scope": "Individual taxpayers",
      "v26": "Not yet announced (last announced rate 7.00% carried forward)",
      "v27": "Not yet announced",
      "status": "NOT YET ANNOUNCED",
      "method": "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",
      "src26": "Not published; carried forward from the prior quarter",
      "src27": "No 2027 quarterly rate published as of 2026-08-12",
      "numeric": {
        "v26": "",
        "v27": ""
      }
    }
  ]
}