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How SumTrue checks its calculators and facts

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A calculator is only useful if its answer is right and you can see why.

How a number is checked1. The official source (statute, regulation or agency page) is opened. 2. The claim, a quote and the date are recorded in the fact log. 3. Unit tests run the calculator against the law's own worked examples. 4. The page shows the rule, its source and the last-verified date.1Official sourceStatute, regulationor agency page2Fact logClaim, quote andthe date checked3Unit testsThe law's ownworked examples4The pageRule, source andlast-verified date How a number is checked1. The official source (statute, regulation or agency page) is opened. 2. The claim, a quote and the date are recorded in the fact log. 3. Unit tests run the calculator against the law's own worked examples. 4. The page shows the rule, its source and the last-verified date.1Official sourceStatute, regulation or agency page2Fact logClaim, quote and the date checked3Unit testsThe law's own worked examples4The pageRule, source and last-verified date
Every number on SumTrue passes these four steps.

1. The math is tested against the law's own examples

Each calculator's arithmetic lives in one engine that every page uses. The engine is tested in three ways:

Worked examples from the sources. Where a regulation or agency gives a worked example, it becomes a test. For instance, the federal overtime regulation 29 CFR 778.110(a) works through an employee paid $12 an hour for 46 hours, who is owed $588.00. SumTrue's overtime calculator must produce exactly $588.00.

Hand-worked cases for each rule. Each rule the engine applies (federal weekly overtime, California daily overtime and double time, the California seventh-day rule) has cases worked out by hand line by line, such as a California week of 14, 8, 8, 8 and 8 hours at $20.00, which must come to $1,000.00.

Random weeks against an independent check. Thousands of random weeks are priced by the engine and by a separate, slower reference that walks the week one minute at a time. On October 26, 2026 the overtime engine passed all 45 tests, including 10,000 random weeks, with no difference of even one cent.

Every case is published, with its inputs, the expected answer, the working and the source, on the test cases page.

2. Money is counted exactly

Computers often store numbers like 0.1 inexactly, which can put a pay total a cent out. SumTrue's engine avoids this: time is counted in whole units small enough to hold any minute exactly, rates are held in ten-thousandths of a dollar, and hours are never rounded before pay is worked out. Each pay line is rounded once, half up to the cent, so the lines always add up to the total shown.

3. Every rule is traced to an official source

Every rule, rate, threshold and date on a page is recorded in a fact register with five things: the claim, the value, the official source it was checked against, the date it was checked, and its status. Official sources mean the statute or regulation itself, a federal or state labor department, or the IRS. Blog posts, other calculators and AI answers are never used as sources.

A claim can go on a page only when its status is verified: the source was opened on the checked date and says what the page says. A claim marked unsourced, wrong or stale is removed or fixed before the page is published.

On the page, each rule shows its last-verified date and a link to the source, so you can check it yourself. The full register is on the fact-check log.

4. Law pages get a second check

Any page that states what a law requires is checked a second time against the primary text before it goes live: wage and hour rules against the statute and labor department guidance, and tax rules against the Internal Revenue Code and IRS guidance. The overtime tax deduction estimator, for example, counts only the extra half of overtime pay required by the federal Fair Labor Standards Act, and leaves out overtime required only by state law or a contract, as 26 U.S.C. 225 and IRS Fact Sheet FS-2026-13 set out.

These checks are done by SumTrue, not by an outside lawyer or accountant. That is why every rule links to its source, and why no page is advice. See the Disclaimer.

5. What the calculators do not cover

Each calculator page lists its own limits. Across the overtime calculators, these are not modeled yet:

  • a regular rate that includes bonuses (29 CFR 778.208). Shift pay in the regular rate (29 CFR 778.207(b)) is worked out only on the shift differential calculator;
  • California alternative workweek schedules and the exemptions in Labor Code 514 and 515;
  • employer rounding of clock times (29 CFR 785.48); the time card counts exact minutes.

6. How the content is made

Pages and code are drafted with the help of software tools, including AI writing and coding assistants. No draft is published until its facts have passed the checks above and the calculator has passed its tests. We do not publish invented statistics, quotes, reviews or credentials.

7. Rechecks and corrections

Rules are rechecked whenever a source announces a change, for example a new IRS fact sheet or a state law taking effect, and each rule's last-verified date shows when its source was last opened. If you report a mistake to hello@sumtrue.com, we check it against the source. If the page is wrong, we fix the page and its tests, update the last-verified date, and add an entry to the fact-check log saying what changed and when.

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