How We Source and Verify Tax Data

Data Sources

We source all tax figures from official government publications. We do not use secondary sources (news articles, other tax websites, AI-generated content) as primary references. Our sources include:

1. Federal income tax brackets and deductions: IRS Revenue Procedure 2025-32 (annual inflation adjustments)
2. OBBBA deduction provisions: The statute text (Public Law 119-1), codified as IRC §224 (tips), §225 (overtime), §70103 (senior bonus deduction)
3. FICA rates and Social Security wage base: Social Security Administration COLA announcements
4. Retirement contribution limits: IRS COLA Notice for the applicable tax year
5. State income tax rates and brackets: Each state's Department of Revenue or Franchise Tax Board official rate schedules
6. Sales and property tax data: State revenue department publications and Census Bureau data
7. ACA subsidy data: HHS Federal Poverty Level guidelines and IRS applicable percentage tables per IRC §36B

Verification Process

Every tax figure in our system carries one of three statuses:

• verified_primary: The figure has been checked against the primary official source document and confirmed correct for the stated tax year.
• verified_secondary: The figure has been cross-referenced with a reliable secondary source but awaits confirmation against the primary document.
• TODO_VERIFY: The figure is a reasonable estimate based on prior-year data or announced changes but has not yet been verified against the published official source.

We maintain an internal verification dashboard tracking individual data points across 51 jurisdictions. An automated publish gate prevents any calculator page from going live if it depends on unverified data.

Calculator Logic

All tax calculations are implemented as pure TypeScript functions with comprehensive unit tests. Each calculator function is tested against official worked examples from IRS publications before deployment. Our test suite includes boundary cases (zero income, negative inputs, phase-out thresholds, filing status exclusions) to prevent errors.

Update Cycle

Tax data is updated annually when the IRS publishes inflation adjustments (typically October/November for the following tax year). OBBBA provisions are monitored for legislative changes. State data is updated as states publish their annual rate schedules.

What We Don't Model

Our calculators deliberately do not model every edge case. Provisions we currently exclude include: AMT, NIIT, education credits, EITC, foreign tax credits, and complex multi-state filing scenarios. Where a calculator has limitations, they are noted on the page.

Correction Policy

If you identify an error in any calculation or data point, contact us at [email protected]. We investigate all reports within 24 hours and publish corrections with clear notes on affected pages. Transparency about errors is more important to us than appearing infallible.

Open Data

All tax figures used by this site are sourced from public government documents and are not proprietary. Source URLs are provided on every calculator page so you can verify figures independently.