[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 2026-11-10 09:00:00 for release on Tuesday, November 10, at 9am ET. The site has no scheduled publishing, so the post goes live when this merges and deploys.
• Cover: a new image of a 2027 tax form (app/public/assets/posts/federal-tax-inflation-adjustments-2027/cover.webp).

Content

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

• How the IRS indexes with the C-CPI-U (182.86 over the 11 published months of the year ending August 31, 2026, up 3.2%), and how PolicyEngine projects amounts the IRS hasn't published.

• 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. Pavel and Ziming have approved it.

The API still serves policyengine-us 2.2.1 through the certified bundle, so the parameter explorer and the app won't show the 2027 values when this publishes. The post's last sentence says so; see the comment below for details.

🤖 Generated with Claude Code

https://claude.ai/code/session_01LqCGPgxDukji8Bhs57c5rH

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Project	Deployment	Actions	Updated
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[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.

[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.