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Data Sources, Methodology and Limits

This site publishes calculators built from federal releases it can cite line by line, and states on every page which releases were used.

Where the numbers come from

Every figure on this site is quoted from one of the 14 federal releases listed below. Each calculator page repeats only the citations that apply to it, so a page about mileage rates does not claim to be sourced from the inflation adjustment release. The full set was last checked on 2026-11-14.

What we deliberately do not estimate

Where a release states a threshold without publishing a rate, we do not invent one. The senior deduction tool reports the phaseout starting point but not a reduced amount. The AMT tool reports the exemption and phaseout starting point but does not compute AMT liability. The Saver's Credit tool checks the income ceiling but states no credit percentage, because the release used here publishes the ceiling only. Rate thresholds for head of household and married filing separately are not published in the source we use, so bracket-based tax is computed only for single and married filing jointly.

Scope of the estimates

These tools cover federal individual income tax, federal payroll and self-employment tax, and selected retirement, health, mileage and gift provisions. They exclude state and local taxes, itemized deductions, capital gains rates, most credits, and most phaseout formulas. Results are illustrations for planning and education, not tax advice, not a tax return, and not a substitute for a qualified professional.

Independence and corrections

The calculators have no affiliation with the IRS, the Social Security Administration or any government agency. If you find a figure that does not match a linked release, please report it so the data file and every generated page can be corrected together. All published values live in a single machine-readable data file, which keeps corrections consistent across the site.

Contact

For corrections or questions about a figure, write to [email protected]. Corrections are applied to the shared data file so every affected page is updated together.

Updates

Last rebuilt and verified: 2026-11-14. Tax year 2026 returns are generally filed in 2027; figures for later tax years will be added only after the relevant agency publishes them.

Data provenance

Every figure on this page appears in the official release listed below. The values were checked against those pages on 2026-11-14. Where a release states a threshold but does not publish a rate, this site reports the threshold and does not estimate the missing value.