2027 Tax Brackets Projection: IRS Inflation Adjustment 3.24% (updated October 18, 2026)

The IRS indexes federal income-tax brackets and the standard deduction with the chained CPI-U (IRC §1(f)): the average C-CPI-U for the twelve months ending August 2026 divided by the prior twelve-month average, each as published in that September's CPI release. With all 11 published months of the window printed (Oct 2025 was never published by BLS because of the federal shutdown), the factor is final: 1.032424 — an adjustment of 3.2424% against 2.275% for 2026. Applied to the 2026 amounts in IRS Rev. Proc. 2025-32 (announced Oct 9, 2025) with the statutory rounding (brackets down to $25, standard deduction to $50), the projected 2027 thresholds are below. The factor was fixed by the August CPI release (Sep 11, 2026); the IRS publishes the official amounts in October.

Single

Rate	2026 (Rev. Proc. 2025-32)	2027 projected	Change
10%	up to $12,400	up to $12,800	+$400
12%	up to $50,400	up to $52,025	+$1,625
22%	up to $105,700	up to $109,125	+$3,425
24%	up to $201,775	up to $208,300	+$6,525
32%	up to $256,225	up to $264,525	+$8,300
35%	up to $640,600	up to $661,350	+$20,750
37%	above the 35% bracket	above the 35% bracket	—
Standard deduction	$16,100	$16,600	+$500

Married filing jointly

Rate	2026 (Rev. Proc. 2025-32)	2027 projected	Change
10%	up to $24,800	up to $25,600	+$800
12%	up to $100,800	up to $104,050	+$3,250
22%	up to $211,400	up to $218,250	+$6,850
24%	up to $403,550	up to $416,625	+$13,075
32%	up to $512,450	up to $529,050	+$16,600
35%	up to $768,700	up to $793,600	+$24,900
37%	above the 35% bracket	above the 35% bracket	—
Standard deduction	$32,200	$33,200	+$1,000

Head of household

Rate	2026 (Rev. Proc. 2025-32)	2027 projected	Change
10%	up to $17,700	up to $18,250	+$550
12%	up to $67,450	up to $69,625	+$2,175
22%	up to $105,700	up to $109,125	+$3,425
24%	up to $201,750	up to $208,275	+$6,525
32%	up to $256,200	up to $264,500	+$8,300
35%	up to $640,600	up to $661,350	+$20,750
37%	above the 35% bracket	above the 35% bracket	—
Standard deduction	$24,150	$24,900	+$750

The factor since the switch to chained CPI

Tax year	Window	Adjustment (as published)	On today's revised data
2018	Sep 2016–Aug 2017	1.747%	1.65%
2019	Sep 2017–Aug 2018	1.941%	1.993%
2020	Sep 2018–Aug 2019	1.589%	1.551%
2021	Sep 2019–Aug 2020	1.001%	1.142%
2022	Sep 2020–Aug 2021	3.115%	2.934%
2023	Sep 2021–Aug 2022	7.081%	7.256%
2024	Sep 2022–Aug 2023	5.402%	5.278%
2025	Sep 2023–Aug 2024	2.789%	2.792%
2026	Sep 2024–Aug 2025	2.275%	2.422%
2027	Sep 2025–Aug 2026	3.242%	3.189%

The IRS uses chained CPI-U values as published in that September's CPI release, and C-CPI-U months are revised for up to a year after they first print. The Sep 2024–Aug 2025 average is therefore taken from the 2025-09-11 release (177.1137); today's revised values average 177.2058. This vintage-true method reproduces the year-over-year change in every published bracket top since 2019 to within rounding — last year's factor recomputes as 2.275%. Chained CPI-U months are published as "initial" values and revised quarterly for up to a year; the current window uses the latest published vintage plus the nowcast month. BLS never published an October 2025 index (federal shutdown): the 12-month average uses the published months, and the payload also carries the factor with that month linearly interpolated. Sources: BLS chained CPI-U via FRED/ALFRED (SUUR0000SA0), IRS Rev. Proc. 2025-32, IRC §1(f), the Nowflation Forecast. Projections, not promises. The COLA is set by the Social Security Administration with the September CPI; I-Bond rates by the Treasury for November 1 and May 1; tax-year amounts by the IRS in a revenue procedure each fall. The IRS indexes from statutory base-year amounts with cumulative factors and rounds once, so chaining from the published 2026 amounts can differ from the official 2027 figures by one rounding step ($25 / $50). Chained CPI-U initial values are revised. Not tax, benefits or investment advice. Every call is graded on the scoreboard after the announcement.