Methodology.

Official values come from primary documents: agency revenue procedures, notices, tables, API data, statutes and state revenue departments. A versioned record contains the value, source URL, saved source evidence, retrieval date, effective period and verification date. A primary-source label describes evidence, not government endorsement.

Dates are part of the number.

Tax-year limits use calendar years. GSA lodging and SNAP tables use federal fiscal years ending September 30. Mileage changes are stored as dated periods, and seasonal lodging uses the actual start and end dates. A year label alone is insufficient for these figures.

Projections use the applicable statute.

For eligible federal tax parameters, IRC section 1(f) uses the average chained CPI-U over the 12 months ending August 31 of the preceding year, divided by the appropriate statutory base-year average. The item’s own law sets the base amount, base year and rounding increment. The 2025 law changes the base for the first two tax boundaries beginning in 2026 and resets the basic standard deduction to its 2025 statutory amounts.

Every projected record identifies the BLS series, observation window, calculation date, bases, rounding, revision caveat and any missing-observation assumption. Historical reconstruction uses retained release-window CPI and reproduces the published 2024-2026 tax brackets. Latest revised BLS data can give different historical results. Official published records take priority over every model comparison.

October 2025 CPI was not published. The current 2027 chained-CPI projection explicitly interpolates that missing month between September and November as an assumption. It is not a BLS observation, and the output remains projected. Retirement uses a different CPI-U rule; wage bases use wage indexing; mileage is an administrative rate. We leave a future figure awaiting publication if its model or source is not verified.

Official releases take priority.

Reviewed promotion preserves source evidence, writes an official file, clears dependent cached pages, refreshes sitemaps, appends the changelog and queues the updated URL for IndexNow. An official file always wins over a projected file, regardless of file ordering.

Calculators explain their scope.

Pure PHP calculations run on a GET request. They validate numeric inputs and display assumptions, exclusions and primary data sources. They provide planning estimates, not return preparation or agency eligibility decisions. Tax tables, special elections, deductions, supplied meals and state rules may change the final result.

Corrections are visible.

Report the page URL, year, source document and the suspected difference through Contact. Changes to published data are recorded in the changelog. Saved source files and local verification reports let the maintainer review how a value was derived.