How we rate sources
Every tax table on this site lists the documents its figures came from, and every document carries a tier. This page is the rule that assigns them — and it is generated from the same code the site uses, so what you read here is what the site actually does.
The rule in one sentence
A source’s tier is determined by what published it — not by how confident we are in the number, and not by the web address. A tier is never typed in by hand and never stored on a record; it is computed from the publisher every time it is shown, which means it cannot be quietly upgraded to make a table look better sourced than it is.
Primary authority
The enacted law, or the revenue agency’s own rate schedule, form or instruction booklet — the document a filer would actually use.
- Statute or session lawDelaware Code Title 30 §1102, on delcode.delaware.gov20 registered domains
- Revenue agency — primary publicationThe FTB’s 2025 California Tax Rate Schedules PDF70 registered domains
Official restatement
Published by the government, but restating figures issued elsewhere: an agency explainer page, or bill text and fiscal notes on a legislature’s site.
- Revenue agency — secondary pageA governor’s office press release announcing a rate cut7 registered domains
- LegislatureAn enrolled bill or fiscal note on a legislature’s own site22 registered domains
Expert secondary
A third party reproducing or analysing the law — legal publishers, accounting firms, and tax policy institutes. Reliable, but not the issuer.
- Legal databaseCornell LII’s reproduction of an Oklahoma administrative rule3 registered domains
- Professional or policy analysisA Tax Foundation state profile, or an EY tax alert23 registered domains
Restatement
News coverage, blogs and calculator sites. Useful for locating a change; never sufficient on its own to establish a figure.
- News, blog or aggregatorA news report or calculator site restating a new rate28 registered domains
Why a government address is not enough
The obvious shortcut — treat any .gov address as authoritative — fails in both directions. Several state revenue agencies do not use a .gov domain at all (floridarevenue.com, revenue.state.mn.us, revenuquebec.ca), and plenty of .gov pages are press releases restating a figure published elsewhere.
So instead, every domain we are willing to cite is listed in the repository with the strongest class it is allowed to claim — 173 domains today. A citation may classify itself more conservatively than its domain allows, never less, and a source from an unlisted domain fails the build. Adding a new one is a deliberate change that has to say what kind of publisher it is.
What a tier does not tell you
A tier rates the document, not our reading of it. A tier-1 source can still be transcribed into a table incorrectly, cited for a figure it does not actually contain, or be the right document for the wrong tax year. The tier tells you how strong the evidence is if we read it correctly; it is not a claim that we did.
Two other labels sit alongside the tiers on each table:
- Provisional — the values are our best current reading but the jurisdiction has not published final figures, or the figures carry forward from the prior year. Treat them as directional.
- Carried forward — the citation is the previous year’s document, shown because this year’s values are unchanged and no new document exists yet. We label these rather than presenting last year’s schedule as though it were this year’s.
Each citation also carries the date we last confirmed the link resolved and still contained the figures cited. That claim is re-checked on a schedule rather than asserted once and left to rot.
What this does not cover yet
Citation coverage is strongest for 2025 and 2026, where an independent review checked every jurisdiction field by field. Earlier years carry the single primary source recorded when the table was built, and some historical entries have no source recorded at all — where that is true, the table says so instead of leaving a blank. TaxMath models a single filer with a simplified rate structure and is an estimator, not tax advice; see Methodology for what the calculator does and does not model, and Corrections for what we have got wrong and fixed.
Checking our work
Open any table on the Tax Tables page and expand its source list. Each entry names the fields it supports, so you can go straight from a number you doubt to the document behind it. If a citation does not say what we say it says, that is a bug worth reporting: feedback [at] taxmath.org.