How we check

We use sources in this order, and each calculator lists the ones it relies on:

• The law itself: the U.S. Code, public laws and state statutes.
• Regulations and official guidance: the Federal Register, IRS revenue procedures, notices and publications, CMS rules.
• Agency data: Bureau of Labor Statistics price indexes, HUD income limits, state revenue department rate tables, National Weather Service forecasts.

We don't copy numbers from other calculators or news articles. When we use a secondary source to find something, we then go to the original and cite that.

Each formula has automated tests, and the site is only published when all of them pass. Where an agency publishes a worksheet, such as the IRS worksheet for a reduced Roth IRA limit, the code follows it step by step, rounding included. The tests pay most attention to the edges: the last dollar before a phase-out, a leap day, the end of a month, a shift that runs past midnight.

Tax brackets, contribution limits and income thresholds change every year. Each page names the year it uses. When new values are published, we update the page and its check date.

Some rules are announced before every detail is final, as with the 2027 changes. In those cases we follow the law and the newest official guidance, and the page says which parts are still proposals or expectations.

A short form can't ask about everything a tax return or an agency can. Our results are estimates built from published rules. They are not advice and not a decision about your case. Where a common situation isn't covered, the page says so.

Tell us what you expected and which page it was. We check it against the source, fix the page if we were wrong, and update its check date.