Projected 2027 federal tax brackets

What's still pending: the twelve months the 2027 figures are built from

The law adjusts tax figures using an average of twelve monthly readings of a price index called the Chained CPI for All Urban Consumers, or C-CPI-U. For tax year 2027 the twelve months run from September 2025 through August 2026. Here is every one of them, with the value, when it was published, and where it came from.

"Vintage" matters more than it looks. The government issues this index first as initial, then revises it to interim, and only finalises it about a year later. The IRS computes from the values as published at the time, so a figure derived from initial readings can move even after every month is out.

The missing month nobody else mentions

October 2025 does not exist. There is no October 2025 value in the published C-CPI-U series: the month is simply absent between September 2025 and November 2025. The documented cause is the 2025 lapse in appropriations, which stopped price collection for October; the scheduled October release (13 November 2025) was cancelled rather than rescheduled, unlike the November 2025 release, which was moved from 10 December to 18 December and did appear.

This matters more than a footnote. The law describes the value for a year as the average of the index “as of the close of the 12-month period ending on August 31” — and one of those twelve months was never measured. Whatever the IRS does about it, and it has not said, an eleven-month average is not the twelve-month average the statute describes. Any site publishing confident 2027 figures today has silently made a decision about this month, and none of them tell you which decision they made.

We will update this page when the IRS or BLS says something on the record about it, and not before.

How this is computed

Three rules do all the work, and all three are in the tax code rather than in anyone's spreadsheet.

1. The twelve months are fixed by statute

“The C-CPI-U for any calendar year is the average of the C-CPI-U as of the close of the 12-month period ending on August 31 of such calendar year.”26 U.S.C. § 1(f)(6)(B) — read the statute

That sentence is what pins the window to September 2025 through August 2026 and no other twelve months. It is also why the professional publishers release their first 2027 estimates in September and not before: the last month of the window is not published until then.

2. The adjustment is measured from a fixed year, not from last year

“The cost-of-living adjustment for any calendar year is the percentage (if any) by which— (i) the C-CPI-U for the preceding calendar year, exceeds (ii) the CPI for calendar year 2016, multiplied by the amount determined under subparagraph (B).”26 U.S.C. § 1(f)(3)(A) — read the statute

This is the part most write-ups get wrong. The law does not take last year's bracket and grow it. It takes the original statutory dollar amount and grows it by the change since 2016, every year, from scratch.

3. The increase is rounded down, in steps of $50

“If any increase determined under paragraph (2)(A), section 63(c)(4), section 68(b)(2) or section 151(d)(4) is not a multiple of $50, such increase shall be rounded to the next lowest multiple of $50.”26 U.S.C. § 1(f)(7)(A) — read the statute

“In the case of a married individual filing a separate return, subparagraph (A) (other than with respect to sections 63(c)(4) and 151(d)(4)(A)) shall be applied by substituting "$25" for "$50" each place it appears.”26 U.S.C. § 1(f)(7)(B) — read the statute

Note what is rounded: the increase, not the final amount, and it is rounded down to the next lowest multiple of $50 rather than to the nearest one. The standard deduction follows the same $50 step under its own provision:

“If any increase under this clause is not a multiple of $50, such increase shall be rounded to the next lowest multiple of $50.”26 U.S.C. § 63(c)(7) (rounding clause), as amended by P.L. 119-21 (One Big Beautiful Bill Act) — read the statute

The known limitation, in plain English

Because the law works cumulatively from a fixed base year, a shortcut that takes the 2026 brackets and multiplies them by one year of inflation is not the same calculation. The 2026 figures have already been rounded down once. Growing an already-rounded number and rounding again can land one $50 step away from what the IRS publishes, on some thresholds but not others. Any projection built that way — including one we might publish here later — is right to the dollar on most lines and can be $50 out on a few. We would rather tell you that up front than present a table that looks more precise than it is.

We can show you the arithmetic but not the answer: the first step is the average of the 12 monthly values over September 2025 through August 2026, and 3 of those values do not exist yet, so there is no average to take. Everything downstream of it — the factor, the thresholds, the standard deduction — is blocked on the same step. The build for this site refuses to render a projected dollar amount while any month is missing; that refusal is a test, not a policy.

Why our number may differ from other people's

As of August 11, 2026, the publishers whose 2027 projections are worth comparing against — Bloomberg Tax, Thomson Reuters, Wolters Kluwer — have not published theirs. That is not an oversight on their part: they wait for the last month of the statutory window, which is the same thing this page is waiting for. When theirs appear, they will be listed here with their figures and their dates, including where they disagree with us.

There is also a category of site worth naming without linking to. Several pages ranking for "2027 tax brackets" today publish a full set of dollar figures derived from a flat inflation rate with no stated window, no month list, and no source. A rate quoted to two decimal places with nothing behind it is not a projection, it is a guess with a table around it. The test to apply to any 2027 figure you find, ours included: can you see which months it used, and can you click through to them?

When the real numbers arrive

The IRS publishes the official tax-year-2027 amounts in a Revenue Procedure. There is no announced date — recent years have landed in the second half of October, and the 2026 figures came out in Rev. Proc. 2025-32 on October 9, 2025. When the 2027 procedure lands, the content on this page is replaced with the official figures — the projection does not quietly turn into a fact, and nothing here flips automatically.

In the meantime, the numbers that are official and final today are the 2026 ones, and they are the ones that govern the return you file next spring: see the official 2026 federal tax brackets.

What you can actually do with this today

• Working out what you take home now: paycheck calculator for your state.
• A bonus coming: bonus tax calculator.
• Reading a W-2 and wondering why the wage boxes disagree: Box 1 vs Box 3 vs Box 5.
• Social Security's 2027 increase runs on a different index and a different window: 2027 COLA estimate and calculator.