Update NH 2025 income tax parameters for I&D tax repeal

[PavelMakarchuk]

Summary

• Add explicit 2025-01-01: 0 rate entry to rate.yaml to show the I&D tax rate is 0 after repeal (complements the existing in_effect: false entry)
• Add TIR 2025-001 repeal reference to disability_age_threshold.yaml and old_age_eligibility.yaml (the 2 remaining files that were missing it)

All 9 NH income tax parameter files now reference TIR 2025-001 confirming the Interest & Dividends tax repeal effective January 1, 2025. The education tax credit (Chapter 77-G) is unchanged for 2025.

Test plan

• All 47 NH tax tests pass

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (1ffb212) to head (19d21ec).
⚠️ Report is 266 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##             main     #7379       +/-   ##
============================================
+ Coverage   71.93%   100.00%   +28.06%     
============================================
  Files        3819         2     -3817     
  Lines       55013        24    -54989     
  Branches      274         0      -274     
============================================
- Hits        39571        24    -39547     
+ Misses      15423         0    -15423     
+ Partials       19         0       -19     

Flag	Coverage Δ
unittests	100.00% <100.00%> (+28.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[PavelMakarchuk]

State Tax Parameter Audit: NH 2025 I&D Tax Repeal

Source

• Document: TIR 2025-001 — I&D Tax Repealed Effective January 1, 2025 (CDN currently returns 403; content verified via NH DOR announcement and McLane Middleton analysis)
• Law: HB 2 (2023 session), signed by Governor Sununu
• Tax year: 2025
• Scope: PR changes only (3 files)

Parameter Value Verification

File	Change	Verified Value	Source	Status
rate.yaml	Add 2025-01-01: 0	0% (tax repealed)	TIR 2025-001, HB 2	✅ CORRECT
disability_age_threshold.yaml	Add TIR 2025-001 reference	N/A (reference only)	—	✅ CORRECT
old_age_eligibility.yaml	Add TIR 2025-001 reference	N/A (reference only)	—	✅ CORRECT

Rate History Verified

Period	Repo Value	Confirmed Value	Status
Before 2023	5%	5% (RSA 77:1)	✅
2023	4%	4% (HB 2 phase-down)	✅
2024	3%	3% (HB 2 phase-down)	✅
2025	0% (PR adds this)	0% (repealed per HB 2)	✅

Defense-in-Depth Check

The repeal is correctly implemented via two independent mechanisms:

1. in_effect.yaml: Already set to false for 2025-01-01 (pre-existing, not in this PR)
2. rate.yaml: This PR adds 0 for 2025-01-01

The formula in nh_income_tax_before_refundable_credits.py checks if p.in_effect first, so the in_effect: false flag alone would zero out the tax. Adding rate: 0 is a good belt-and-suspenders approach that makes the parameter tree self-documenting.

TIR Reference Consistency

After this PR, all 8 income tax parameter files under gov/states/nh/tax/income/ reference TIR 2025-001:

File	Had TIR Before PR	Has TIR After PR
rate.yaml	✅	✅
in_effect.yaml	✅	✅
exemptions/amount/base.yaml	✅	✅
exemptions/amount/blind_addition.yaml	✅	✅
exemptions/amount/disabled_addition.yaml	✅	✅
exemptions/amount/old_age_addition.yaml	✅	✅
exemptions/disability_age_threshold.yaml	❌	✅ (this PR)
exemptions/old_age_eligibility.yaml	❌	✅ (this PR)

The education tax credit (tax/credits/education/rate.yaml) is under Chapter 77-G (separate from Chapter 77 I&D tax) and correctly does not reference TIR 2025-001.

Pre-existing Issues (not from this PR)

1. Metadata unit: currency-USD on age parameters: disability_age_threshold.yaml and old_age_eligibility.yaml both specify unit: currency-USD but store age values (65). Should be unit: year.

2. TIR 2025-001 PDF URL returns 403: The URL https://www.revenue.nh.gov/sites/g/files/ehbemt736/files/documents/2025-001-technical-information-release-repeal.pdf currently returns "Access Denied" from the NH DOR CDN. This affects all 8 files that reference it. The content is still available via the NH DOR news page.

3. Broken statute URLs: The gencourt.state.nh.us URLs (e.g., RSA 77:1, 77:4, 77:5) redirect to gc.nh.gov and then 404. These are referenced across multiple files.

Verdict

All changes are correct. Clean, minimal PR that properly documents the NH I&D tax repeal for 2025. No parameter value issues found.

---

Audit performed by comparing PR changes against TIR 2025-001, HB 2, NH DOR announcements, and existing repo parameter files.

[DTrim99]

State Tax Parameter Audit

Source

• TIR 2025-001: NH Interest and Dividends Tax Repeal
• Statutes: RSA Chapter 77 (Repealed), RSA Chapter 77-G (Education Tax Credit)
• Tax year: 2025
• Scope: PR changes only

---

✅ All Parameter Values Verified Correct

Parameter	Repo Value	Official Source	Status
Tax rate 2020	5%	TIR 2025-001	✓
Tax rate 2023	4%	TIR 2025-001	✓
Tax rate 2024	3%	TIR 2025-001	✓
Tax rate 2025 (NEW)	0%	TIR 2025-001 - "repealed for taxable periods beginning after December 31, 2024"	✓
in_effect 2025	false	RSA Chapter 77 - "[Repealed by 2021, 91:189, II, eff. Jan. 1, 2025.]"	✓
Base exemption (single)	$2,400	Filing thresholds confirmed in TIR	✓
Base exemption (joint)	$4,800	Filing thresholds confirmed in TIR	✓
Old age eligibility	65	Consistent with DP-10 forms	✓
Disability age threshold	65	Consistent with DP-10 forms	✓

---

✅ URL Updates Verified Working

Old URL	New URL	Status
gencourt.state.nh.us/rsa/html/V/77/77-1.htm	gc.nh.gov/rsa/html/V/77/77-mrg.htm	✓ Working
gencourt.state.nh.us/rsa/html/V/77/77-4.htm	gc.nh.gov/rsa/html/V/77/77-mrg.htm	✓ Working
gencourt.state.nh.us/rsa/html/V/77/77-5.htm	gc.nh.gov/rsa/html/V/77/77-mrg.htm	✓ Working
gencourt.state.nh.us/rsa/html/NHTOC/NHTOC-V-77-G.htm	gc.nh.gov/rsa/html/NHTOC/NHTOC-V-77-G.htm	✓ Working

---

✅ Metadata Fixes Verified Correct

File	Old Unit	New Unit	Correct?
disability_age_threshold.yaml	currency-USD	year	✓ Yes - value is age 65, not dollars
old_age_eligibility.yaml	currency-USD	year	✓ Yes - value is age 65, not dollars

---

Summary

All changes in this PR are correct. The PR properly:

1. Adds the 2025 rate of 0% reflecting the I&D tax repeal effective January 1, 2025
2. Adds TIR 2025-001 references to the two remaining parameter files (disability_age_threshold.yaml, old_age_eligibility.yaml)
3. Fixes incorrect unit metadata on age parameters (was currency-USD, now correctly year)
4. Updates statute URLs from the old gencourt.state.nh.us domain to the new gc.nh.gov domain

🤖 Automated audit by Claude Code