Tax Calculator

Overview

Federal income tax estimator with two filing statuses. Uses progressive bracket accumulation. State-specific interactive breakdowns use a separate component (IncomeSliderVisualization) on state tax pages.

Formula

Progressive bracket tax (marginal slices):

tax = 0, prev = 0
For each [limit, rate] in brackets:
  if income > prev:
    tax += (min(income, limit) − prev) × rate
    prev = limit
  else break

effectiveRate = (tax / income) × 100
takeHome = income − tax

2024 brackets — Single (28:36:src/components/calculators/TaxCalculator.tsx):

Up to	Rate
$11,000	10%
$44,725	12%
$95,375	22%
$182,100	24%
$231,250	32%
$578,125	35%
∞	37%

Married filing jointly uses doubled/lowest-bracket limits (37:45:src/components/calculators/TaxCalculator.tsx).

State variants (`IncomeSliderVisualization`)

Used on per-state tax calculator pages for federal + state + FICA breakdown.

Federal (2025 single filer piecewise) — 40:48:src/components/calculators/IncomeSliderVisualization.tsx:

Piecewise linear function with breakpoints at $11,600, $47,150, $100,525, $191,950, $243,725, $609,350.

State tax:

stateTax = income × stateRate

stateRate from STATE_TAX_RATES[stateCode] or optional stateTaxRate prop (top marginal simplified rates).

FICA:

socialSecurity = min(income, 168600) × 0.062
medicare = income × 0.0145
fica = socialSecurity + medicare

Combined:

total = federal + state + fica
effectiveRate = (total / income) × 100
takeHome = income − total

Inputs

TaxCalculator: annual income, filing status (single / married).

IncomeSliderVisualization: income slider $10k–$500k, state code/name, optional override rate.

Calculation steps

TaxCalculator:

User clicks Calculate.
Select bracket table by filing status.
Walk brackets; round tax and take-home.

IncomeSliderVisualization:

Recompute on income change (live).
Calculate federal via piecewise function.
Apply flat state marginal rate.
Add FICA with SS wage base cap.

Outputs

TaxCalculator: estimated tax, effective rate, take-home.

IncomeSliderVisualization: federal/state/FICA amounts, bar chart, total burden, effective rate, take-home, insight text.

Assumptions

No deductions, credits, or standard/itemized adjustments in either component.
State tax = flat top marginal rate × full income (not progressive state brackets).
TaxCalculator uses 2024 brackets; IncomeSliderVisualization uses 2025 federal breakpoints— they are not aligned.
FICA only in state visualization; not in base TaxCalculator.

Data sources

Hardcoded bracket tables in components.
STATE_TAX_RATES map (51 jurisdictions) in IncomeSliderVisualization.tsx.
FORMULA_TAX display string from FinancialAioContent.

Known limitations

Base calculator is federal-only and on-demand (button).
State pages use different federal year and simplified state rates vs. TaxCalculator.
No payroll withholding, AMT, or self-employment tax.

Files touched

src/components/calculators/TaxCalculator.tsx
src/components/calculators/IncomeSliderVisualization.tsx
State tax route pages (mount IncomeSliderVisualization)
src/lib/federal-tax-brackets.ts (shared 2026 bracket source)

Fixed in Phase 1.1b (2026-06-13 — commit pending review)

Federal brackets unified in src/lib/federal-tax-brackets.ts using 2026 thresholds from IRS Rev. Proc. 2025-32. Both TaxCalculator.tsx and IncomeSliderVisualization.tsx import calculateFederalTax() from this module.