Add Illinois Senior Citizens Real Estate Tax Deferral Program

[hua7450]

Summary

Closes #6780. Implements the Illinois Senior Citizens Real Estate Tax Deferral Program (SCRETD).

This program allows qualified seniors (65+) to defer property taxes as a loan from the State of Illinois. The deferred amounts accrue interest and must be repaid upon sale, transfer, or death.

Regulatory Authority

• Primary Statute: 320 ILCS 30 - Senior Citizens Real Estate Tax Deferral Act
• Income Definition: 320 ILCS 25/3.07
• Recent Amendment: SB1821 (expanded income limits)
• IDOR Publication: PIO-64

Eligibility Requirements

Age Requirement (320 ILCS 30/2)

• Must be 65+ years old by June 1 of the application year

Income Limits (320 ILCS 30/2, SB1821)

Tax Year	Income Limit
2006-2011	$50,000
2012-2021	$55,000
2022-2024	$65,000
2025	$75,000
2026	$77,000
2027+	$79,000

Benefit Calculation

Parameter	Value	Source
Maximum Annual Deferral	$7,500	320 ILCS 30/3, PIO-64

Formula: deferral = min(real_estate_taxes, $7,500) when eligible

Files Added

Parameters (3 files)

policyengine_us/parameters/gov/states/il/idor/scretd/
├── age_threshold.yaml        # Primary applicant age (65)
├── income_limit.yaml         # Household income limits by year
└── max_annual_deferral.yaml  # $7,500 annual limit

Variables (4 files)

policyengine_us/variables/gov/states/il/idor/scretd/
├── il_scretd_age_eligible.py      # Person-level age eligibility (65+)
├── il_scretd_income_eligible.py   # Tax unit income eligibility
├── il_scretd_eligible.py          # Combined eligibility
└── il_scretd_deferral_amount.py   # Deferral amount (loan, not benefit)

Tests (5 files, 37 test cases)

policyengine_us/tests/policy/baseline/gov/states/il/idor/scretd/
├── il_scretd_age_eligible.yaml      # 4 cases
├── il_scretd_income_eligible.yaml   # 12 cases
├── il_scretd_eligible.yaml          # 4 cases
├── il_scretd_deferral_amount.yaml   # 6 cases
└── integration.yaml                 # 11 cases

Non-Simulatable Rules

The following program rules cannot be implemented (require data not available in point-in-time simulation):

Rule	Reason
Interest rate (3%/6%)	Requires tracking cumulative interest across multiple years
80% equity limit	Requires property fair market value, mortgage balance, and cumulative prior deferrals
Surviving spouse continuation (age 55+)	Only applies to continuing an existing deferral after primary applicant's death
3-year ownership requirement	Cannot verify ownership duration
Annual reapplication	Cannot enforce annual renewal

Example Calculation

Case: Eligible senior in 2024

Input:
  - Age: 70 years
  - Employment income: $50,000
  - Real estate taxes: $10,000

Calculation:
  - Age check: 70 >= 65 = true
  - Income check: $50,000 <= $65,000 = true
  - Eligible: true AND true = true
  - Deferral: min($10,000, $7,500) = $7,500

Output:
  - il_scretd_eligible: true
  - il_scretd_deferral_amount: $7,500

Implementation Notes

1. Entity Level: Tax unit (property-owner based program)
2. Income Definition: Uses irs_gross_income as proxy for household income per 320 ILCS 25/3.07
3. Age Aggregation: Uses add() > 0 pattern to check if ANY tax unit member is age-eligible
4. Loan, Not Benefit: The deferral amount is a loan that accrues interest and must be repaid - this is noted in the variable's formula comments

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (8649b3a) to head (7261e11).
⚠️ Report is 17 commits behind head on main.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files            3         4    +1     
  Lines           39        51   +12     
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+ Hits            39        51   +12     

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

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