Revert #8911: restore OK retirement subtraction for IRC 401 pensions pre-2022 (#9009)

[PavelMakarchuk]

Fixes #9009. Reverts #8911 (which addressed #8830).

Problem

#8911 excluded private (IRC §401) employer pensions from ok_pension_subtraction before 2022, on the premise that the 2021 Schedule 511-A line 6 instructions did not list §401 plans. That premise is false. The 2021 Form 511 Packet, page 17 — the same document cited by private_pension_qualifies.yaml — lists as the first qualifying source "An employee pension benefit plan under IRC Section 401". The 2022 packet's line-6 text is word-for-word identical; §401 was not added in 2022.

Effect on the originating taxsim record (2021 MFJ, pensions $38,458): PolicyEngine returned ok_pension_subtraction = $0 (should be 2 × $10,000 = $20,000) and overstated ok_income_tax by a flat $1,000 (5% × $20,000) for any pre-2022 MFJ record with ≥$10k/person private pension.

Fix

Reverts #8911: drops the private_pension_qualifies gate and restores min_(p.pension_limit, pensions) per person.

Tests

• Unit: added a 2021 case confirming a private (IRC §401) pension qualifies for the $10,000 exclusion. Removed the incorrect 2021 "private → $0" case introduced by Exclude private (IRC 401) employer pensions from OK retirement subtraction before 2022 #8911.
• Integration: added the taxsim New York #1083 case → ok_pension_subtraction $20,000, ok_agi $61,891, ok_income_tax $2,005 (matches TaxAct and TAXSIM-35 to the dollar).

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (ff39625) to head (82133f8).
⚠️ Report is 12 commits behind head on main.

Additional details and impacted files

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##              main     #9016   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files            1         1           
  Lines           18        14    -4     
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- Hits            18        14    -4     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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[hua7450]

Verified against both the statute and the form instructions — approving.

The revert's premise is confirmed at two levels:

1. Instructions: the 2021 Form 511 Packet, page 17, Schedule 511-A line 6 lists as its first qualifying source "An employee pension benefit plan under IRC Section 401" — and the 2022 packet's line-6 text is word-for-word identical. Nothing was added in 2022.
2. Statute: 68 O.S. § 2358(A)(13)(c) defines "retirement benefits" as distributions from "(1) an employee pension benefit plan which satisfies the requirements of Section 401 of the Internal Revenue Code" (first in the statutory list, unchanged since the mid-2000s amendments); (13)(d) sets the $10,000-per-individual limit for 2006+; (13)(b)(5) removes any income cap from 2010 onward. So #8911's gate was wrong under the primary source as well as the operational one.

Model correctness note: min_($10,000, taxable_pension_income) per person correctly reproduces the combined effect of ¶8 (line 5, government pensions) and ¶13 (line 6, other retirement) because (13)(d) caps the combined total at $10,000 per individual — the merged single-cap model is exact, not a simplification.

Revert hygiene: no residual references to private_pension_qualifies; the deleted parameter cited only form packets with reference titles asserting "§401 not listed" about the page that lists it, so the revert also removes misinformation from reference metadata.

Tests: taxsim #1083 arithmetic verified independently — federal AGI 2×(19,228.76+21,716.92) + 85%×24,944.88 SS = 103,094.51; OK AGI = 103,095 − 21,203 SS exclusion − 20,000 pension subtraction = 61,891.36 (matches TAXSIM-35 to the cent); OK tax ≈ 2,004.6 (matches TaxAct to the dollar).

CI fully green (35/35).