Editorial policy

What counts as a source

Accepted sources are constitutions and statutes published by the legislature, regulations, and pages, bulletins or forms published by the state revenue department, tax commission or, for the District of Columbia, the Office of Tax and Revenue. Each rule in a state model stores the source URL, a citation, a verifiable passage or document supporting the figure and the date it was read. Commercial summaries, tax-preparation blogs and encyclopedias may help locate a statute but are never cited and never supply a number. When a statewide figure does not exist because the rule is set locally (an Oklahoma county’s assessment percentage, a Pennsylvania county’s ratio, a New York municipality’s level of assessment), the calculator asks for that one input and says why, rather than filling it with an average.

Verification cadence

Some figures are fixed in statute until the legislature changes them, such as Tennessee’s 25% residential assessment or Alabama’s 10% Class III ratio. Others are re-published every year: Florida’s Save Our Homes percentage, Michigan’s inflation rate multiplier, California’s inflation factor, indexed homestead amounts and the District’s homestead deduction. Each state model records the tax year it describes and the last day its most time-limited figure applies, and the page shows the date its sources were last read. About six weeks before that last day the figure is due for a fresh reading of the agency notice; until a successor figure has been read in the source itself, the calculator does not apply a lapsed number to a new year. Every model is also re-read when a legislative session ends.

How the arithmetic is checked

Every state and DC has at least one worked example: a sample home run through the cited rules by hand, step by step, from value to assessment to exemptions to the final bill. The worksheet on that state’s page must reproduce the hand result to the cent, and a difference of even one cent holds back any change to the site until the rule or the arithmetic is corrected. The same example is also typed into the page’s own worksheet, field by field, and the total shown there must equal the hand calculation. If a figure on a page does not match the statute or agency notice it cites, that is an error to report through the corrections form below.

Automation and AI disclosure

The publisher uses AI tools to help locate primary sources, draft explanations and write the software and tests. Those tools do not decide figures: a statutory amount enters a model only together with a primary document supporting it, and the arithmetic is fixed by tests. Explanations are written for this site, describe the cited rule in plain words and avoid repeating the same text across states.

How corrections work

Readers flag errors through the corrections form: a misstated rate or ratio, a rule the legislature has since amended, a citation link that no longer resolves, or a worksheet that miscalculates. Every state page links to the form with its own address already entered. Reports are stored in a private queue with the page, the type of problem and the message. A confirmed error is fixed in the model and its test, the affected page’s visible updated date changes, and the sitemap date for that page changes with it. Reports that turn out to describe a local option or an individual eligibility question are answered by pointing to the relevant local office where a reply address was given.

Independence

No assessor, lender, title company or advertiser reviews or pays for content. The site carries no sponsored placements, and no page links to sister sites in exchange for links back.