Update Colorado 2025 Individual Income Tax Model

## Summary

Update the Colorado individual income tax model for tax year 2025. This includes updating parameter values, adding 2025 references to all parameter files, and creating new 2025 integration tests.

**Primary Source**: [2025 Colorado Individual Income Tax Filing Guide (Book 104)](https://tax.colorado.gov/sites/tax/files/documents/Book104_2025.pdf)

---

## Parameter Updates Required

### 1. Income Tax Rate (`rate.yaml`) ✅ Values OK, Needs Reference
- **Current**: 2025-01-01: 0.044 (4.4%) - **CORRECT**
- **Action**: Add 2025 104 Book reference

### 2. EITC Match (`credits/eitc/match.yaml`) ⚠️ Verify Value
- **Current**: 2025-01-01: 0.35 (35%)
- **2025 Finding**: Some sources indicate 50% match for 2025
- **Action**: Verify correct 2025 rate from Form DR 0104CR, add 2025 reference
- **Source**: [Colorado EITC Info](https://tax.colorado.gov/EITC)

### 3. Sales Tax Refund - MAJOR UPDATE NEEDED

#### 3a. Scale Amounts (`credits/sales_tax_refund/amount/scale.yaml`) 🔴 Missing 2025
Add 2025 values (Single filer amounts):
| AGI Range | 2024 Amount | 2025 Amount |
|-----------|-------------|-------------|
| $0-52,000 | $177 | $19 |
| $52,001-105,000 | $240 | $25 |
| $105,001-168,000 | $277 | $29 |
| $168,001-233,000 | $323 | $35 |
| $233,001-299,000 | $350 | $37 |
| $299,001+ | $565 | $59 |

Joint filers get 2x single amounts.

**Source**: [State Sales Tax Refund](https://tax.colorado.gov/income-tax-topics-state-sales-tax-refund)

#### 3b. Flat Amount Enabled (`credits/sales_tax_refund/amount/flat_amount_enabled.yaml`)
- Add: `2025-01-01: false` (scale-based, not flat)

### 4. Child Tax Credit (`credits/ctc/`)

#### 4a. CTC Amounts by Filing Status 🔴 Missing 2025
Files to update:
- `credits/ctc/amount/single.yaml`
- `credits/ctc/amount/joint.yaml`
- `credits/ctc/amount/head_of_household.yaml`
- `credits/ctc/amount/separate.yaml`
- `credits/ctc/amount/surviving_spouse.yaml`

**2025 Finding**: Maximum $1,200 per child ages 0-5
- Verify income thresholds and amounts from DR 0104CN

### 5. Family Affordability Tax Credit (`credits/family_affordability/`) 🔴 Missing 2025

#### 5a. Base Amount (`amount.yaml`)
- **Current 2024**: $3,200 (base for young child)
- **2025 Finding**: $3,273 for ages 0-5, $2,455 for ages 6-16
- **Action**: Update for inflation adjustment

#### 5b. Age Multiplier (`age_multiplier.yaml`)
- **Current 2024**: 1.0 for ages 0-5, 0.75 for ages 6-16
- **2025 Calculation**: $2,455 / $3,273 ≈ 0.75 (same multiplier)
- **Action**: Verify multiplier unchanged, add 2025 reference

### 6. CDCC Match (`credits/cdcc/match.yaml`) 📝 Reference Only
- **Action**: Add 2025 104 Book reference

### 7. Low Income CDCC (`credits/cdcc/low_income/`) 📝 Reference Only
Files to update:
- `child_age_threshold.yaml`
- `federal_agi_threshold.yaml`
- `max_amount.yaml`
- `rate.yaml`

### 8. Pension/Social Security Subtraction (`subtractions/pension/`)
Files to update with 2025 references:
- `age_threshold/older.yaml`
- `age_threshold/younger.yaml`
- `cap/older.yaml` (currently $24,000)
- `cap/younger.yaml`
- `social_security_subtraction_available.yaml`

### 9. Military Retirement Subtraction (`subtractions/military_retirement/`)
- `age_threshold.yaml`
- `max_amount.yaml`

### 10. CollegeInvest Contribution (`subtractions/collegeinvest_contribution/max_amount.yaml`)
- Add 2025 reference

### 11. Charitable Contribution (`subtractions/charitable_contribution/adjustment.yaml`)
- Add 2025 reference

### 12. ABLE Contribution (`subtractions/able_contribution/cap.yaml`)
- Add 2025 reference

### 13. Federal Deduction Addback (`additions/federal_deductions/`)
- `agi_threshold.yaml`
- `exemption.yaml`
- `itemized_only.yaml`

### 14. QBI Deduction Addback (`additions/qualified_business_income_deduction/agi_threshold.yaml`)
- Add 2025 reference

### 15. Income Qualified Senior Housing Credit (`credits/income_qualified_senior_housing/`)
- `age_limit.yaml`
- `income_threshold.yaml`
- `reduction/*.yaml` (amount, increment, max_amount, start)

### 16. Care Worker Credit (`credits/care_worker/`) 
- Note: Takes effect 2026 - add 2025 reference for continuity
- `amount/joint.yaml`
- `amount/non_joint.yaml`
- `income_limit/joint.yaml`
- `income_limit/non_joint.yaml`

### 17. TABOR Cash Back (`credits/tabor/`)
- `single.yaml` - currently only has 2021 value
- `joint.yaml`
- **Action**: Verify if TABOR cash back mechanism still applies in 2025 (separate from sales tax refund)

---

## New Tests Required

Create 2025 integration tests in `policyengine_us/tests/policy/baseline/gov/states/co/tax/income/`:

### 1. `integration.yaml` - Add 2025 test cases
```yaml
- name: Colorado 2025 single filer with EITC and sales tax refund
  period: 2025
  input:
    state_code: CO
    filing_status: SINGLE
    employment_income: 30_000
    # ... additional inputs
  output:
    co_income_tax: [expected value]
    co_eitc: [expected value]
    co_sales_tax_refund: [expected value]
```

### 2. Credit-specific 2025 tests:
- `credits/eitc/co_eitc.yaml` - 2025 test cases
- `credits/sales_tax_refund/co_sales_tax_refund.yaml` - 2025 brackets
- `credits/ctc/co_ctc.yaml` - 2025 amounts
- `credits/family_affordability/co_family_affordability_credit.yaml` - 2025 amounts

---

## Reference Sources

All parameter files need the following 2025 reference added:
```yaml
- title: 2025 Colorado Individual Income Tax Filing Guide, 104 Book
  href: https://tax.colorado.gov/sites/tax/files/documents/Book104_2025.pdf
```

Additional sources:
- [DR 0104CR - Tax Credits](https://tax.colorado.gov/sites/tax/files/documents/DR_0104CR_2025.pdf) (for credit-specific pages)
- [DR 0104CN - Child Tax Credit Instructions](https://tax.colorado.gov/sites/tax/files/documents/DR_0104CN_2025.pdf)
- [State Sales Tax Refund Info](https://tax.colorado.gov/income-tax-topics-state-sales-tax-refund)
- [CTC & EITC Info](https://tax.colorado.gov/ctc-eitc)

---

## Checklist

### Parameters - Values
- [ ] Sales tax refund 2025 amounts (scale.yaml)
- [ ] Sales tax refund flat_amount_enabled (add 2025-01-01: false)
- [ ] EITC match - verify 35% vs 50%
- [ ] CTC amounts - verify 2025 values
- [ ] Family Affordability amount - inflation adjustment
- [ ] TABOR cash back - verify mechanism for 2025

### Parameters - References Only
- [ ] rate.yaml
- [ ] eitc/match.yaml
- [ ] cdcc/match.yaml
- [ ] cdcc/low_income/*.yaml
- [ ] pension/*.yaml
- [ ] military_retirement/*.yaml
- [ ] collegeinvest_contribution/max_amount.yaml
- [ ] charitable_contribution/adjustment.yaml
- [ ] able_contribution/cap.yaml
- [ ] additions/federal_deductions/*.yaml
- [ ] additions/qualified_business_income_deduction/*.yaml
- [ ] income_qualified_senior_housing/*.yaml
- [ ] care_worker/*.yaml
- [ ] ctc/age_threshold.yaml
- [ ] ctc/eligible_child.yaml
- [ ] ctc/ctc_matched_federal_credit.yaml
- [ ] ctc/rate/*.yaml
- [ ] ctc/amount/*.yaml
- [ ] family_affordability/age_multiplier.yaml
- [ ] family_affordability/reduction/*.yaml
- [ ] sales_tax_refund/age_threshold.yaml
- [ ] sales_tax_refund/amount/multiplier.yaml
- [ ] sales_tax_refund/magi_sources.yaml
- [ ] tabor/*.yaml

### Tests
- [ ] Add 2025 integration tests
- [ ] Add 2025 unit tests for credits with value changes
- [ ] Verify all existing tests still pass

---

## Implementation Notes

1. **No logic changes expected** - only parameter value and reference updates
2. **EITC verification critical** - the 35% vs 50% match rate significantly impacts results
3. **Sales tax refund amounts decreased significantly** from 2024 to 2025 (e.g., $177 → $19 for lowest bracket)
4. **Family Affordability Credit** amounts appear to be inflation-indexed

---

## Files Count Summary

- **Parameter files to update**: ~55 files
- **Test files to update/add**: ~10 files
- **Total estimated changes**: 100+ line changes across 65+ files

AGI Range	2024 Amount	2025 Amount
$0-52,000	$177	$19
$52,001-105,000	$240	$25
$105,001-168,000	$277	$29
$168,001-233,000	$323	$35
$233,001-299,000	$350	$37
$299,001+	$565	$59

Update Colorado 2025 Individual Income Tax Model #7054

Description

Summary

Parameter Updates Required

1. Income Tax Rate (rate.yaml) ✅ Values OK, Needs Reference

2. EITC Match (credits/eitc/match.yaml) ⚠️ Verify Value

3. Sales Tax Refund - MAJOR UPDATE NEEDED

3a. Scale Amounts (credits/sales_tax_refund/amount/scale.yaml) 🔴 Missing 2025

3b. Flat Amount Enabled (credits/sales_tax_refund/amount/flat_amount_enabled.yaml)

4. Child Tax Credit (credits/ctc/)

4a. CTC Amounts by Filing Status 🔴 Missing 2025

5. Family Affordability Tax Credit (credits/family_affordability/) 🔴 Missing 2025

5a. Base Amount (amount.yaml)

5b. Age Multiplier (age_multiplier.yaml)

6. CDCC Match (credits/cdcc/match.yaml) 📝 Reference Only

7. Low Income CDCC (credits/cdcc/low_income/) 📝 Reference Only

8. Pension/Social Security Subtraction (subtractions/pension/)

9. Military Retirement Subtraction (subtractions/military_retirement/)

10. CollegeInvest Contribution (subtractions/collegeinvest_contribution/max_amount.yaml)

11. Charitable Contribution (subtractions/charitable_contribution/adjustment.yaml)

12. ABLE Contribution (subtractions/able_contribution/cap.yaml)

13. Federal Deduction Addback (additions/federal_deductions/)

14. QBI Deduction Addback (additions/qualified_business_income_deduction/agi_threshold.yaml)

15. Income Qualified Senior Housing Credit (credits/income_qualified_senior_housing/)

16. Care Worker Credit (credits/care_worker/)

17. TABOR Cash Back (credits/tabor/)

New Tests Required

1. integration.yaml - Add 2025 test cases

2. Credit-specific 2025 tests:

Reference Sources

Checklist

Parameters - Values

Parameters - References Only

Tests

Implementation Notes

Files Count Summary

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions

1. Income Tax Rate (`rate.yaml`) ✅ Values OK, Needs Reference

2. EITC Match (`credits/eitc/match.yaml`) ⚠️ Verify Value

3a. Scale Amounts (`credits/sales_tax_refund/amount/scale.yaml`) 🔴 Missing 2025

3b. Flat Amount Enabled (`credits/sales_tax_refund/amount/flat_amount_enabled.yaml`)

4. Child Tax Credit (`credits/ctc/`)

5. Family Affordability Tax Credit (`credits/family_affordability/`) 🔴 Missing 2025

5a. Base Amount (`amount.yaml`)

5b. Age Multiplier (`age_multiplier.yaml`)

6. CDCC Match (`credits/cdcc/match.yaml`) 📝 Reference Only

7. Low Income CDCC (`credits/cdcc/low_income/`) 📝 Reference Only

8. Pension/Social Security Subtraction (`subtractions/pension/`)

9. Military Retirement Subtraction (`subtractions/military_retirement/`)

10. CollegeInvest Contribution (`subtractions/collegeinvest_contribution/max_amount.yaml`)

11. Charitable Contribution (`subtractions/charitable_contribution/adjustment.yaml`)

12. ABLE Contribution (`subtractions/able_contribution/cap.yaml`)

13. Federal Deduction Addback (`additions/federal_deductions/`)

14. QBI Deduction Addback (`additions/qualified_business_income_deduction/agi_threshold.yaml`)

15. Income Qualified Senior Housing Credit (`credits/income_qualified_senior_housing/`)

16. Care Worker Credit (`credits/care_worker/`)

17. TABOR Cash Back (`credits/tabor/`)

1. `integration.yaml` - Add 2025 test cases