Our Methodology

Data Sources

All data on PlainTaxData comes directly from official Internal Revenue Service sources. We reference the following IRS publications and announcements for each tax parameter:

  • Tax brackets: IRS Revenue Procedures (annual inflation adjustments, e.g., Rev. Proc. 2024-61).
  • Standard deductions: IRS Publication 501 — Dependents, Standard Deduction, and Filing Information.
  • Capital gains rates: IRS Revenue Procedures + Publication 550 — Investment Income and Expenses.
  • Retirement contribution limits: IRS annual announcements (IR-2024-285 and similar IR notices).
  • Tax credits (EITC, CTC, CDCTC): IRS Publications 596, 972, and 503.
  • Alternative Minimum Tax: IRS Form 6251 instructions and associated revenue procedures.

How We Present the Data

We extract tax parameters from IRS publications each tax year and store them in a structured format. For each filing status and year, we record:

  • Marginal tax bracket thresholds and rates for ordinary income.
  • Long-term capital gains rate thresholds (0%, 15%, 20%).
  • Standard deduction amounts by filing status and age.
  • Retirement account contribution limits (401k, IRA, Roth IRA, HSA, FSA).
  • EITC income thresholds and maximum credit amounts by number of qualifying children.
  • Child Tax Credit phase-in and phase-out ranges.
  • AMT exemption amounts and phase-out thresholds.

Tax Estimator Methodology

The interactive tax estimator computes estimated federal income tax liability using the following approach:

  • Adjusted Gross Income (AGI) = gross income minus above-the-line deductions you specify.
  • Taxable income = AGI minus the greater of standard deduction or itemized deductions entered.
  • Tax computed by applying each bracket's marginal rate to the income within that bracket.
  • Credits (EITC, CTC) applied to reduce tax liability.
  • Capital gains taxed separately at long-term rates where applicable.

This is a simplified estimate. It does not account for state taxes, self-employment tax, the Net Investment Income Tax (NIIT), AMT, phase-outs of certain deductions, or every credit and deduction scenario. Use it for rough planning — not as a substitute for tax software or a tax professional.

Accuracy and Updates

The IRS adjusts many tax parameters annually for inflation. We update our database each year when the IRS publishes its annual revenue procedure for inflation adjustments, typically in October or November. While we strive for accuracy, tax law changes frequently — always verify figures against current IRS publications before making tax decisions.

Processing Pipeline

Our ETL pipeline builds the PlainTaxData database through a structured extraction and validation process:

  • Download IRS Revenue Procedures, publications, and IR announcements for each tax year as they are released
  • Extract tax bracket thresholds, standard deductions, credit amounts, and contribution limits from the official IRS text
  • Validate extracted figures by cross-referencing multiple IRS sources (Revenue Procedures vs. Publications vs. Form instructions)
  • Store each parameter with its tax year, filing status, and source IRS document reference for traceability
  • Build the interactive tax estimator's calculation engine from the validated parameter set

No tax data is fabricated or interpolated. Every figure comes directly from an official IRS publication or announcement. Where the IRS has not yet published a figure for a given tax year, we do not estimate or project it.

Important Disclaimer

PlainTaxData is an informational resource only. It does not constitute tax, legal, or financial advice. Tax situations are individual — consult a qualified tax professional (CPA, EA, or tax attorney) for advice specific to your circumstances.

Not Affiliated

PlainTaxData is not affiliated with the Internal Revenue Service or any government agency. We are an independent data portal presenting official IRS-published tax reference data in a more accessible format.