Update Georgia 2025 Individual Income Tax Model

[DTrim99]

Summary

Updates Georgia's individual income tax model for tax year 2025 based on the official IT-511 Instructions Booklet.

Fixes #7284

Key Changes

Tax Rate Correction

• 2025 rate corrected to 5.19% (was incorrectly projected as 5.29%)
• Updated projected rates for 2026-2028 to maintain 0.1% annual reduction schedule:
  • 2026: 5.09%
  • 2027: 4.99%
  • 2028: 4.89%

References Added

Added 2025 IT-511 Instructions Booklet references to all parameters:

• Tax rate brackets (all 5 filing statuses)
• Standard deduction amounts
• Dependent exemption ($4,000)
• Retirement income exclusion (ages 62-64: $35,000; 65+: $65,000)
• Retirement income earned income cap ($5,000)
• Military retirement exclusion ($17,500 base + $17,500 conditional)
• CDCC credit rate (50% of federal)
• Itemizer credit ($300)
• Low income credit thresholds
• Subtractions list
• Path2College 529 Plan deduction

Values Verified (Unchanged from 2024)

Parameter	Value
Standard Deduction (MFJ)	$24,000
Standard Deduction (Single/MFS/HoH/QSS)	$12,000
Dependent Exemption	$4,000
Retirement Exclusion (62-64/disabled)	$35,000
Retirement Exclusion (65+)	$65,000
Retirement Exclusion Earned Income Cap	$5,000
Military Retirement Base Exclusion	$17,500
Military Retirement Additional Exclusion	$17,500
Military Retirement Earned Income Threshold	$17,500
CDCC Rate	50% of federal
Itemizer Credit	$300/taxpayer
Low Income Credit Threshold	AGI < $20,000

Tests Added

• 2025 single filer flat tax test (50,000 * 0.0519 = 2,595)
• 2025 joint filer flat tax test (100,000 * 0.0519 = 5,190)
• 2024 single filer flat tax test (50,000 * 0.0539 = 2,695) for comparison

Files Changed

• 5 tax rate parameter files (joint, single, separate, head_of_household, surviving_spouse)
• 11 retirement/military exclusion parameter files
• 4 credit parameter files (CDCC, itemizer, low income)
• Standard deduction and dependent exemption parameters
• Subtractions list parameter
• 529 plan deduction variable reference
• Test file with new 2025 test cases

Reference

• 2025 IT-511 Individual Income Tax Booklet

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (a57bc47) to head (4226fa5).
⚠️ Report is 1122 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##              main     #7285    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           25         1    -24     
  Lines          297         9   -288     
==========================================
- Hits           297         9   -288     

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

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.