[DTrim99]

Adds "Federal Tax Inflation Adjustments for Tax Year 2027", following the 2025 post.

• Post: app/src/data/posts/articles/federal-tax-inflation-adjustments-2027.md.
• Entry: posts.json, dated 2026-11-09 11:00:00 for release on Monday, November 9, at 11am ET. The site has no scheduled publishing, so the post goes live when this merges and deploys.
• Cover: reuses the 2025 post's image (fed_tax_inflation_adjustments.webp).

Content

• The IRS's Rev. Proc. 2026-35 amounts for tax year 2027, released November 5, 2026.

• How the IRS indexes, with chained CPI and statutory rounding.

• A table comparing PolicyEngine's projected 2027 standard deductions with the IRS values:

  Filing status	Projected	IRS
  Single	16,550	16,600
  Joint	33,150	33,200
  Head of household	24,850	24,925
  Separate	16,550	16,600

• Across the bracket, standard deduction, EITC, capital gains and AMT amounts, the official 2027 increases were about 9% larger than projected at the median. The 2025 post found about 10%.

• A list of every provision updated, with links to its parameter file.

The projections are the values policyengine-us main gave before the update, computed from main at 39265d9be0. The IRS values are from policyengine-us PR #10683.

Before merging

PolicyEngine/policyengine-us#10683 must merge first, so the model and the linked parameter files carry the 2027 values. It's CI-green and awaiting review.

🤖 Generated with Claude Code

https://claude.ai/code/session_01LqCGPgxDukji8Bhs57c5rH

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The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated
policyengine-calculator-next	Ready	Preview	Nov 9, 2026 6:18pm UTC
policyengine-website	Ready	Preview	Nov 9, 2026 6:18pm UTC

[DTrim99]

@MaxGhenis Please approve but don't merge. I'll merge it myself once PolicyEngine/policyengine-us#10683 merges, since this post describes the 2027 values that PR adds to the model.

[MaxGhenis]

Thanks, David. Every 2027 IRS amount in the post matches Rev. Proc. 2026-35, Table 1's projections match PolicyEngine/policyengine-us@39265d9be0, and the amounts the PR body names give the same 9% median. The preview renders the table and the new cover, and the cover's head-of-household example adds up: a $24,925 deduction, $3,844 of tax and a $2,300 CTC. The PR description still says the post reuses the 2025 image. At PolicyEngine/policyengine-us@58e9fc0160, the head of PolicyEngine/policyengine-us#10683, all 22 linked parameter files carry the IRS's 2027 values, including the $945 long-term care limit for ages 41 to 50.

The post's last sentence links the parameter explorer, which reads api.policyengine.org/us/metadata. That API still serves our 2027 projections, such as $16,550 for single filers and $24,850 for heads of household, and this command prints 16550.0 today:

curl -s https://api.policyengine.org/us/metadata | jq '.result.parameters["gov.irs.deductions.standard.amount.SINGLE"].values["2027-01-01"]'

Once it prints 16600.0, I'd move the posts.json date (November 9, 11:00) to that day and merge.

[MaxGhenis]

In its news release, IR-2026-133, the IRS gives the date and counts almost 70 provisions. The suggestion links that release, drops the ordinal from "November 5", says "bracket thresholds" to match line 26, and cuts the "millions of households" clause, which gives no count.

Suggested change

On November 5th, 2026, the Internal Revenue Service (IRS) released its annual inflation adjustments for over sixty federal tax parameters for tax year 2027 in [Revenue Procedure 2026-35](https://www.irs.gov/pub/irs-drop/rp-26-35.pdf). These include the standard deduction, income tax thresholds, and the Earned Income Tax Credit (EITC), which affect the millions of American households who file taxes each year. PolicyEngine has updated its US model to reflect these changes.

On November 5, 2026, the Internal Revenue Service (IRS) [released](https://www.irs.gov/newsroom/irs-releases-tax-inflation-adjustments-for-tax-year-2027-taxpayers-continue-to-benefit-from-the-working-families-tax-cuts) its annual inflation adjustments to almost 70 tax provisions for tax year 2027 in [Revenue Procedure 2026-35](https://www.irs.gov/pub/irs-drop/rp-26-35.pdf). These include the standard deduction, income tax bracket thresholds, and the Earned Income Tax Credit (EITC). PolicyEngine has updated its US model to reflect these changes.

[MaxGhenis]

With one heading, the table of contents lists only "Overview". I'd add ## How the IRS amounts compare with our projections above line 9 and ## Other indexed provisions above line 20.

[MaxGhenis]

BLS published no October 2025 value, so the 182.86 average covers the other 11 months of the year ending August 31, 2026. The suggestion names the missing month and makes Congress the subject of the first sentence.

Suggested change

Since the passage of the [Tax Cuts and Jobs Act of 2017](https://www.congress.gov/115/plaws/publ97/PLAW-115publ97.pdf#page=7) ([26 U.S.C. § 1(f)(3)](https://www.law.cornell.edu/uscode/text/26/1#f_3)), federal income tax provisions are indexed using the Chained Consumer Price Index for All Urban Consumers (C-CPI-U). The C-CPI-U averaged 182.86 over the 12 months ending August 31, 2026, up 3.2% from 177.11 over the 12 months ending August 31, 2025.

In the [Tax Cuts and Jobs Act of 2017](https://www.congress.gov/115/plaws/publ97/PLAW-115publ97.pdf#page=7) ([26 U.S.C. § 1(f)(3)](https://www.law.cornell.edu/uscode/text/26/1#f_3)), Congress began indexing federal income tax provisions to the Chained Consumer Price Index for All Urban Consumers (C-CPI-U). The Bureau of Labor Statistics published no C-CPI-U value for October 2025. Over the other 11 months of the year ending August 31, 2026, the C-CPI-U averaged 182.86, up 3.2% from 177.11 over the 12 months ending August 31, 2025.

[MaxGhenis]

Line 7 says we apply the same statutory rounding rules, and we don't always. Under section 63(c)(7)(B)(ii), the IRS rounds the increase over the 2025 amount, so heads of household get $23,625 plus $1,300, or $24,925. For most amounts, policyengine-core instead grows the latest IRS amount and rounds the whole result, so our standard deduction projections land on multiples of $50, such as $24,850. Some parameters, such as the EITC's maximum investment income, set no rounding rule. We also took several 2027 values from CBO forecasts, as their parameter files note, including the EITC phase-out start, the AMT 28% threshold and the refundable CTC. The suggestion leaves rounding out, names two of those, and makes users the subject of the last sentence.

Suggested change

PolicyEngine estimates these indexed amounts for years the IRS has not yet published, using the Congressional Budget Office's [inflation projections](https://www.cbo.gov/data/budget-economic-data#4) and observed C-CPI-U and applying the same statutory rounding rules. This allows users to calculate their household net income and analyze policy proposals for future years before the IRS announces the official values.

For years the IRS has not yet published, PolicyEngine projects these amounts. For most, we grow the latest IRS amount by the C-CPI-U, using observed values and then the Congressional Budget Office's [inflation projections](https://www.cbo.gov/data/budget-economic-data#4). For a few, including the EITC phase-out thresholds and the AMT 28% bracket threshold, we use CBO's projections of the amounts themselves. Users can then calculate household net income and analyze policy proposals for years before the IRS publishes official values.

[MaxGhenis]

No 2026 post exists, so "previous years" points to one year. The suggestion names the amounts behind the 9%, as the PR body does, and drops "slightly", since the median gives the size.

Suggested change

As in [previous years](/us/research/federal-tax-inflation-adjustments-2025), the IRS adjustments were slightly larger than our projections across most indexed provisions; the official increases were about 9% larger at the median. For example, we projected that the standard deduction for single filers would rise $450, from $16,100 in 2026 to $16,550 in 2027; the IRS set it at $16,600, a $500 increase. Table 1 shows the standard deduction for each filing status.

As it did for [tax year 2025](/us/research/federal-tax-inflation-adjustments-2025), the IRS raised most indexed amounts by more than we projected. Across the bracket, standard deduction, EITC, capital gains, and AMT amounts, the IRS's increases exceeded our projected increases by about 9% at the median. For example, we projected that the standard deduction for single filers would rise $450, from $16,100 in 2026 to $16,550 in 2027; the IRS set it at $16,600, a $500 increase. Table 1 shows the standard deduction for each filing status.

[MaxGhenis]

The IRS has set both amounts, so "are scheduled to" can go, and line 22 already opens with "In addition". The suggestion leads with the 2027 amounts, gives the verbs to Congress and the IRS, and drops the comma after "section 70104)". Under section 24(i)(3), the IRS rounds each increase. With bases of $1,400 and $2,200, rounding each increase or each amount gives the same multiple of $100, so the new last sentence matches the statute and changes no amount.

Suggested change

In addition, both indexed amounts of the Child Tax Credit (CTC) are scheduled to rise in 2027. The maximum refundable portion, which the [Tax Cuts and Jobs Act of 2017](https://www.congress.gov/115/plaws/publ97/PLAW-115publ97.pdf#page=21) (Public Law 115-97, section 11022) set at $1,400 per child and indexed for inflation, rises from $1,700 in 2026 to $1,800 in 2027. The maximum credit, which [H.R. 1, the One Big Beautiful Bill Act](https://www.congress.gov/119/plaws/publ21/PLAW-119publ21.pdf#page=90) (Public Law 119-21, section 70104), raised to $2,200 and indexed for inflation after 2025, rises from $2,200 in 2026 to $2,300 in 2027. Both amounts round down to the next lowest multiple of $100.

The IRS raised both indexed amounts of the Child Tax Credit (CTC) for 2027: the maximum refundable portion from $1,700 to $1,800, and the maximum credit from $2,200 to $2,300. Congress set the refundable portion at $1,400 per child in the [Tax Cuts and Jobs Act of 2017](https://www.congress.gov/115/plaws/publ97/PLAW-115publ97.pdf#page=21) (Public Law 115-97, section 11022) and indexed it for inflation. Congress raised the maximum credit to $2,200 in [H.R. 1, the One Big Beautiful Bill Act](https://www.congress.gov/119/plaws/publ21/PLAW-119publ21.pdf#page=90) (Public Law 119-21, section 70104) and indexed it for inflation after 2025. For both, the IRS rounds each increase down to a multiple of $100 ([26 U.S.C. § 24(i)(3)](https://www.law.cornell.edu/uscode/text/26/24#i_3)).

[MaxGhenis]

Under section 3.15(3) of the Rev. Proc., only unmarried filers other than surviving spouses get $2,100. Surviving spouses get $1,700, as the parameter file has it.

Suggested change

	- [Additional standard deduction for the aged or blind](https://github.com/PolicyEngine/policyengine-us/blob/main/policyengine_us/parameters/gov/irs/deductions/standard/aged_or_blind/amount.yaml) ($1,700, or $2,100 for unmarried filers)
	- [Additional standard deduction for the aged or blind](https://github.com/PolicyEngine/policyengine-us/blob/main/policyengine_us/parameters/gov/irs/deductions/standard/aged_or_blind/amount.yaml) ($1,700, or $2,100 for unmarried filers other than surviving spouses)

[MaxGhenis]

From 2027, Maine sets its standard deduction "equal to the federal standard deduction, subject to the phase-out under subsection 2" (36 M.R.S. § 5124-C(1-D)). We already compute it that way, so Maine's own aged-or-blind amount doesn't enter any 2027 calculation. Arizona's Department of Revenue adjusts the state's amounts "in the same manner" as the federal basic standard deduction (A.R.S. § 43-1041(H)), from the same 2025 bases, so Arizona's 2027 amounts equal the IRS's. The suggestion also says who updated Arizona's amounts.

Suggested change

	Two state amounts follow the federal values and were updated with them: Arizona's standard deduction and Maine's additional standard deduction for the aged or blind.
	Arizona's Department of Revenue adjusts the state's standard deduction for inflation the same way the IRS adjusts the federal one, so we updated Arizona's 2027 amounts to match. From 2027, Maine sets its standard deduction equal to the federal one, subject to Maine's own phase-out.

[MaxGhenis]

Recent post titles use sentence case.

Suggested change

	"title": "Federal Tax Inflation Adjustments for Tax Year 2027",
	"title": "Federal tax inflation adjustments for tax year 2027",

[DTrim99]

@MaxGhenis Thanks for the review. I'm applying all of your suggestions. On the API check, waiting for /us/metadata to print 16600.0 would hold this post for weeks, so I'd rather not wait for it.

Why the API won't show the 2027 values soon

• api.policyengine.org serves policyengine-us 2.2.1 (released 9/15). It takes its model from policyengine.py's certified bundle, which pins policyengine-us 2.2.1, policyengine-core 3.33.3, spm-calculator 1.0.0 and the US data release populace-us-2024-spm-20260915.
• That data release claims compatibility only with policyengine-us >=2.0.0,<2.3. Moving the bundle to a current release needs a recertification or a US data rebuild with the newer model. Anthony found that a plain recertification fails because so much has changed, so that's your and Anthony's work, and it could take weeks.
• policyengine-us 2.2.2, which shipped today on release/2.2.x, adds only the spm-calculator 1.1 pin and CBO's 2036 CPI-U points to 2.2.1. It doesn't include #10683.
• So merging Update federal tax parameters to the 2027 amounts in Rev. Proc. 2026-35 policyengine-us#10683 alone doesn't change the API. The API will show $16,600 only once the bundle moves to a policyengine-us release that includes it.
• Backporting #10683 to the 2.2 line as 2.2.3 is possible but a real porting job. A trial merge conflicts in about a dozen parameter and test files, three files #10683 edits don't exist on 2.2.1, and it would need its own review and another bundle certification. We'd need to scope that with you and Anthony first.

Plan for the post

• Don't hold it for the API. I've reworded the last sentence so it doesn't promise that the parameter explorer or the app shows the 2027 values yet:

  The 2027 values are available now in the latest release of our policyengine-us Python package. Our parameter explorer and web app still use an earlier version of the model and will show them in a future update.

• Publish when Update federal tax parameters to the 2027 amounts in Rev. Proc. 2026-35 policyengine-us#10683 merges, and move the posts.json date (now November 9, 11:00) to that day before merging.