How the credits are computed

Every calculator and page reads three data files: the federal parameters for 2025 and 2026, the rules of the 50 states and the District of Columbia, and the California table for 2025. Each figure carries the official address it was read at and the date (November 1, 2026). No amount is typed into a page: the pages call the same engine as the calculators. Automated tests check the engine against the official tables.

1. The federal credit

The engine applies the method of the IRS table, not the bare formula. For an income, it takes the $50 band that contains it, computes the credit at the middle of the band with the rate, maximum and phase-out of the year, and rounds to the dollar. Two rules of the printed table are reproduced: a band that contains the earned income amount gives the full maximum, and the phase-out starts with the first band that lies entirely above the threshold. With these rules the engine matches every one of the 1,366 lines and 10,928 amounts of the 2025 table in the Form 1040 instructions, a test run on every build. The credit is computed at earned income and, when AGI differs and is at or above the phase-out start, at AGI, and the smaller is kept, as on the IRS worksheet. The investment income limit, the age range without a child and the Social Security number test are applied; the relationship and residency tests for a child cannot be checked and are stated as conditions.

2. State credits

Each state is recorded with its rate or formula for 2025 and 2026, whether the credit is refundable, whether it accepts ITIN filers and its minimum age without a child. A percentage credit is applied to the federal amount; where a state covers younger workers or ITIN filers, the engine computes the federal amount as if the federal test were met, as those states do. California is read line by line from the Franchise Tax Board table and Young Child Tax Credit worksheet; Minnesota follows Schedule M1CWFC; Washington follows RCW 82.08.0206 with its 2025 amounts; Oklahoma uses the 2020 federal parameters of Rev. Proc. 2019-44, as its Form 511-EIC does; New York City follows the rate worksheet of Form IT-215. A nonrefundable credit is capped at the state tax you enter. Tests check examples against the published state figures, such as the Connecticut maximums and the California table.

3. Child tax credit and income tax

The child tax credit follows section 24 as amended in 2025 and Schedule 8812: $2,200 per child under 17, refundable up to $1,700 per child and 15% of earned income above $2,500, reduced by $50 per $1,000 above $200,000 or $400,000. To split it, the engine estimates regular income tax on AGI minus the standard deduction, with the brackets of the year. It ignores itemized deductions, the new deductions of the 2025 law for tips, overtime, car loan interest and seniors, other credits, and the alternative refundable formula for three or more children.

4. Not yet published

When a state publishes its amounts for a year with its forms, and the forms are not out, the calculator shows "not yet published" for that state and year. For other states, the 2026 rule is the law as we read it on November 1, 2026; a change enacted later will be added with its date. On that date, the following were not computed or not confirmed: the District of Columbia formula for workers without a child, Maryland's county credits, Minnesota's add-on for qualifying children aged 18 or over, New York's household credit subtraction, Oklahoma's option based on the previous year's earned income, and any New Mexico rate change for 2026.

5. State sources read

6. Federal sources read

7. What the site does not do

• It does not prepare, file or check a return, and gives no tax advice.
• It does not decide whether a child is your qualifying child.
• It keeps nothing you type: the calculators run in your browser.

Method version of November 1, 2026. A figure that looks wrong: contact.