Published Rates: September 2026, and the Quarter Beginning October 1.
August 2026
On August 21, 2026, the Internal Revenue Service published the applicable federal rates for September 2026 in Rev. Rul. 2026-17, and announced in IR-2026-98 that the section 6621 interest rates for the calendar quarter beginning October 1, 2026 are unchanged. Both are set out below as published.
Section 7520 rate — September 2026.
The rate under section 7520 for September 2026 — the rate used to value an annuity, an interest for life or for a term of years, or a remainder or reversionary interest — is 5.40 percent. Rev. Rul. 2026-17, Table 5 (Rate Under Section 7520 for September 2026), released Aug. 21, 2026. The ruling is scheduled for publication in a forthcoming Internal Revenue Bulletin; as of this writing the bulletin citation is not yet available.
The August 2026 rate was 5.20 percent, unchanged from July. Internal Revenue Service, “Section 7520 interest rates” (listing 5.2 percent for July 2026 (Rev. Rul. 2026-12) and 5.2 percent for August 2026 (Rev. Rul. 2026-13)).
Applicable federal rates — September 2026.
Table 1 of Rev. Rul. 2026-17 sets the following applicable federal rates for September 2026. Rev. Rul. 2026-17, Table 1 (Applicable Federal Rates (AFR) for September 2026); see I.R.C. § 1274(d).
| Attribute | Annual | Semiannual | Quarterly | Monthly |
|---|---|---|---|---|
| Short-term AFR | 4.18% | 4.14% | 4.12% | 4.10% |
| Short-term 110% AFR | 4.60% | 4.55% | 4.52% | 4.51% |
| Short-term 120% AFR | 5.03% | 4.97% | 4.94% | 4.92% |
| Short-term 130% AFR | 5.45% | 5.38% | 5.34% | 5.32% |
| Mid-term AFR | 4.49% | 4.44% | 4.42% | 4.40% |
| Mid-term 110% AFR | 4.94% | 4.88% | 4.85% | 4.83% |
| Mid-term 120% AFR | 5.40% | 5.33% | 5.29% | 5.27% |
| Mid-term 130% AFR | 5.85% | 5.77% | 5.73% | 5.70% |
| Mid-term 150% AFR | 6.77% | 6.66% | 6.61% | 6.57% |
| Mid-term 175% AFR | 7.92% | 7.77% | 7.70% | 7.65% |
| Long-term AFR | 5.12% | 5.06% | 5.03% | 5.01% |
| Long-term 110% AFR | 5.65% | 5.57% | 5.53% | 5.51% |
| Long-term 120% AFR | 6.16% | 6.07% | 6.02% | 5.99% |
| Long-term 130% AFR | 6.69% | 6.58% | 6.53% | 6.49% |
The adjusted AFRs under section 1288(b) for September 2026 are 3.16 percent short-term, 3.40 percent mid-term, and 3.88 percent long-term, each on annual compounding. Rev. Rul. 2026-17, Table 2 (Adjusted AFR for September 2026); see I.R.C. § 1288(b). The adjusted federal long-term rate for the month is 3.88 percent, and the long-term tax-exempt rate under section 382(f) — the highest of the adjusted federal long-term rates for the current month and the prior two months — is likewise 3.88 percent. Rev. Rul. 2026-17, Table 3 (Rates Under Section 382 for September 2026).
The low-income housing credit percentages under section 42(b)(1) for buildings placed in service during September 2026 are 8.12 percent for the 70 percent present value credit and 3.48 percent for the 30 percent present value credit, subject to the 9 percent floor of section 42(b)(2) for non-federally subsidized new buildings placed in service after July 30, 2008. Rev. Rul. 2026-17, Table 4 (Appropriate Percentages Under Section 42(b)(1) for September 2026).
Interest rates — quarter beginning October 1, 2026.
Rates are unchanged from the current quarter. IR-2026-98, “Interest rates remain the same for the fourth quarter of 2026” (Aug. 21, 2026) (announcing that Rev. Rul. 2026-15 will appear in Internal Revenue Bulletin 2026-36, dated Aug. 31, 2026). The federal short-term rate determined under section 1274(d) during July 2026, rounded to the nearest full percent on a daily-compounding basis, is 4 percent. Rev. Rul. 2026-15 (“The federal short-term rate, rounded to the nearest full percent, based on daily compounding determined during the month of July 2026 is 4 percent.”), citing Rev. Rul. 2026-13, 2026-32 I.R.B. 132 (rates taking effect Aug. 1, 2026); see I.R.C. § 6621(a)(1), (a)(2), (b), (c). From that figure:
| Attribute | Quarter beginning October 1, 2026 |
|---|---|
| Overpayments (noncorporate) | 7% |
| Corporate overpayments | 6% |
| Corporate overpayment portion exceeding $10,000 | 4.5% |
| Underpayments (all taxpayers) | 7% |
| Large corporate underpayments (§ 6621(c)) | 9% |
| Section 6603 deposits (§ 6603(d)(4)) | 4% |
The 7 percent underpayment rate also governs the additions to tax for failure to pay estimated tax under sections 6654 and 6655 for the fourth calendar quarter. Rev. Rul. 2026-15, citing I.R.C. §§ 6654(a)(1), 6655(a)(1). Interest under these rates compounds daily pursuant to section 6622; the daily compound interest factors for annual rates of 4.5, 6, 7, and 9 percent appear in Tables 14, 17, 19, and 23 of Rev. Proc. 95-17. I.R.C. § 6622; Rev. Rul. 2026-15; Rev. Proc. 95-17, 1995-1 C.B. 566, 569, 571, 575; see also Notice 88-59, 1988-1 C.B. 546.
This note reports published federal rates for general information. It is not legal or tax advice for any particular person. Rates change monthly and quarterly; confirm the current figure against the governing revenue ruling before relying on it, and note that whether and how any rate applies to a given transaction or liability turns on the facts and on the applicable law.
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