Work & Money
How accurate are our calculators?
Don't take our word for it. Below, our calculation code is run against figures printed in official IRS and Social Security publications, and the results are published as they come out.
23 of 23 checks match the official figures
Run automatically every time this site is built. A mismatch fails our pre-release tests, so you should never see one here.
Live checks against official figures
Each row takes a figure printed by the IRS or the Social Security Administration (or a hand calculation that follows an official worksheet step by step, shown under the check) and compares it with what our engine produces for the same inputs. These are the same engines that power the paycheck calculator, the W-4 calculator, the bonus tax calculator and the EITC calculator.
Federal withholding tables
We rebuild the 2026 annual percentage-method tables from the 2026 tax brackets and standard deductions, then compare every row (wage threshold, base amount and rate) with the tables we transcribed from Publication 15-T. A single mistyped digit in either shows up as a mismatch.
| Check | Expected (from source) | Our calculation | Result |
|---|---|---|---|
| Standard table, single or married filing separately | 8 rows | 8 of 8 match | ✓ Match |
| How: Every row of the annual percentage-method table (Worksheet 1A), as transcribed from Pub 15-T. Source: IRS Publication 15-T (2026). | |||
| Standard table, married filing jointly | 8 rows | 8 of 8 match | ✓ Match |
| How: Every row of the annual percentage-method table (Worksheet 1A), as transcribed from Pub 15-T. Source: IRS Publication 15-T (2026). | |||
| Standard table, head of household | 8 rows | 8 of 8 match | ✓ Match |
| How: Every row of the annual percentage-method table (Worksheet 1A), as transcribed from Pub 15-T. Source: IRS Publication 15-T (2026). | |||
| Form W-4 Step 2 checkbox table, single or married filing separately | 8 rows | 8 of 8 match | ✓ Match |
| How: Every row of the annual percentage-method table (Worksheet 1A), as transcribed from Pub 15-T. Source: IRS Publication 15-T (2026). | |||
| Form W-4 Step 2 checkbox table, married filing jointly | 8 rows | 8 of 8 match | ✓ Match |
| How: Every row of the annual percentage-method table (Worksheet 1A), as transcribed from Pub 15-T. Source: IRS Publication 15-T (2026). | |||
| Form W-4 Step 2 checkbox table, head of household | 8 rows | 8 of 8 match | ✓ Match |
| How: Every row of the annual percentage-method table (Worksheet 1A), as transcribed from Pub 15-T. Source: IRS Publication 15-T (2026). | |||
Paycheck withholding worksheet
Hand calculations that follow Publication 15-T Worksheet 1A line by line, compared with our paycheck engine.
| Check | Expected (from source) | Our calculation | Result |
|---|---|---|---|
| Withholding per paycheck: $60,000 salary, single, paid every two weeks, 2020-or-later W-4 with no entries | $193.08 | $193.08 | ✓ Match |
| How: Annual wages $60,000 − line 1g $8,600 = $51,400. Standard single table row $19,900–$57,900: $1,240 + 12% × ($51,400 − $19,900) = $5,020 a year. ÷ 26 pay periods = $193.08. Source: IRS Publication 15-T (2026). | |||
| Withholding per paycheck: $120,000 salary, married filing jointly, paid monthly, no W-4 entries | $836.67 | $836.67 | ✓ Match |
| How: Annual wages $120,000 − line 1g $12,900 = $107,100. Standard married table row $44,100–$120,100: $2,480 + 12% × ($107,100 − $44,100) = $10,040 a year. ÷ 12 = $836.67. Source: IRS Publication 15-T (2026). | |||
| Withholding per paycheck: $60,000 salary, single, Step 2 box checked, paid every two weeks | $337.88 | $337.88 | ✓ Match |
| How: No line 1g subtraction. Step 2 single table row $33,250–$60,900: $2,900 + 22% × ($60,000 − $33,250) = $8,785 a year. ÷ 26 = $337.88. Source: IRS Publication 15-T (2026). | |||
Income tax brackets
Tax on a round taxable income, worked out slice by slice from the published bracket thresholds, compared with our tax engine.
| Check | Expected (from source) | Our calculation | Result |
|---|---|---|---|
| 2026 tax on $100,000 of taxable income, single | $16,712.00 | $16,712.00 | ✓ Match |
| How: 10% × $12,400 + 12% × ($50,400 − $12,400) + 22% × ($100,000 − $50,400) = $1,240 + $4,560 + $10,912. Source: IRS Rev. Proc. 2025-32. | |||
| 2026 tax on $200,000 of taxable income, married filing jointly | $33,424.00 | $33,424.00 | ✓ Match |
| How: 10% × $24,800 + 12% × ($100,800 − $24,800) + 22% × ($200,000 − $100,800) = $2,480 + $9,120 + $21,824. Source: IRS Rev. Proc. 2025-32. | |||
| 2027 tax on $100,000 of taxable income, single | $16,541.50 | $16,541.50 | ✓ Match |
| How: 10% × $12,800 + 12% × ($52,025 − $12,800) + 22% × ($100,000 − $52,025) = $1,280 + $4,707 + $10,554.50. Source: IRS Rev. Proc. 2026-35. | |||
| 2027 tax on $200,000 of taxable income, married filing jointly | $33,083.00 | $33,083.00 | ✓ Match |
| How: 10% × $25,600 + 12% × ($104,050 − $25,600) + 22% × ($200,000 − $104,050) = $2,560 + $9,414 + $21,109. Source: IRS Rev. Proc. 2026-35. | |||
Social Security and Medicare
Payroll tax caps and thresholds from the Social Security Administration and the IRS, compared with our engine.
| Check | Expected (from source) | Our calculation | Result |
|---|---|---|---|
| Most an employee pays in 2026 Social Security tax ($250,000 salary) | $11,439.00 | $11,439.00 | ✓ Match |
| How: 6.2% × the 2026 wage base of $184,500. Source: SSA 2026 COLA fact sheet. | |||
| 2026 Medicare tax on a $250,000 salary, single | $4,075.00 | $4,075.00 | ✓ Match |
| How: 1.45% Medicare tax (SSA 2026 fact sheet) × $250,000 + 0.9% Additional Medicare Tax × ($250,000 − $200,000) = $3,625 + $450. Source: IRS Topic 560 (Additional Medicare Tax). | |||
Earned Income Tax Credit
The 2026 and 2027 maximum credits and phase-out end points printed in Rev. Procs. 2025-32 and 2026-35, compared with our EITC engine.
| Check | Expected (from source) | Our calculation | Result |
|---|---|---|---|
| 2026 maximum credit with 0 / 1 / 2 / 3+ children | $664 / $4,427 / $7,316 / $8,231 | $664 / $4,427 / $7,316 / $8,231 | ✓ Match |
| How: Section 4.06 table: maximum amount of credit. Source: IRS Rev. Proc. 2025-32. | |||
| Income where the 2026 credit ends, all filing statuses except married filing jointly (0 / 1 / 2 / 3+ children) | $19,540 / $51,593 / $58,629 / $62,974 | $19,540 / $51,593 / $58,629 / $62,974 | ✓ Match |
| How: Section 4.06 table: completed phaseout amount, all other filing statuses. Source: IRS Rev. Proc. 2025-32. | |||
| Income where the 2026 credit ends, married filing jointly (0 / 1 / 2 / 3+ children) | $26,820 / $58,863 / $65,899 / $70,244 | $26,820 / $58,863 / $65,899 / $70,244 | ✓ Match |
| How: Section 4.06 table: completed phaseout amount, married filing jointly. Source: IRS Rev. Proc. 2025-32. | |||
| 2027 maximum credit with 0 / 1 / 2 / 3+ children | $685 / $4,573 / $7,552 / $8,496 | $685 / $4,573 / $7,552 / $8,496 | ✓ Match |
| How: Section 3.06 table: maximum amount of credit. Source: IRS Rev. Proc. 2026-35. | |||
| Income where the 2027 credit ends, all filing statuses except married filing jointly (0 / 1 / 2 / 3+ children) | $20,164 / $53,277 / $60,519 / $65,002 | $20,164 / $53,277 / $60,519 / $65,002 | ✓ Match |
| How: Section 3.06 table: completed phaseout amount, all other filing statuses. Source: IRS Rev. Proc. 2026-35. | |||
| Income where the 2027 credit ends, married filing jointly (0 / 1 / 2 / 3+ children) | $27,684 / $60,787 / $68,029 / $72,512 | $27,684 / $60,787 / $68,029 / $72,512 | ✓ Match |
| How: Section 3.06 table: completed phaseout amount, married filing jointly. Source: IRS Rev. Proc. 2026-35. | |||
Bonus (supplemental wage) withholding
The federal flat rates for bonuses, compared with our bonus tax engine.
| Check | Expected (from source) | Our calculation | Result |
|---|---|---|---|
| Federal withholding on a $10,000 bonus paid separately (optional flat rate) | $2,200.00 | $2,200.00 | ✓ Match |
| How: 22% flat rate on supplemental wages up to $1 million in the year. Source: IRS Publication 15, section 7 (supplemental wages). | |||
| Federal withholding on a $1.5 million bonus (first supplemental pay of the year) | $405,000.00 | $405,000.00 | ✓ Match |
| How: Optional 22% on the first $1,000,000 + mandatory 37% × $500,000 above $1 million = $220,000 + $185,000. Source: IRS Publication 15, section 7 (supplemental wages). | |||
What these checks do and don't show
- They show the arithmetic is right. For the inputs shown, our code reaches the same figure as the official source: to the cent for dollar amounts (to the dollar where the IRS rounds), and row for row for tables.
- They catch typing errors. We type the tax tables in from the IRS publications. Rebuilding the withholding tables independently from the brackets means a single wrong digit shows up as a mismatch.
- They don't make an estimate exact for you. Your real paycheck also depends on your employer's payroll system, your benefits, your W-4 and your state's rules. Our pay stub checker helps you compare the two.
- They aren't tax advice. We aren't CPAs or enrolled agents. See our disclaimer.
What runs before every release
Nothing goes live until all of these pass:
- Calculation tests (68 test files). Every calculator's engine is tested with worked examples, edge cases (zero, caps, thresholds, the last cent of a bracket) and the official figures above.
- Table integrity tests. Published tax tables are re-derived from the rates and thresholds they come from.
- Build tests. Every page is checked for broken internal links, titles, descriptions, structured data and indexing rules.
- Browser tests. More than 100 key pages, including every calculator, are opened in a real browser at phone, tablet and desktop sizes, checked for errors, layout and basic accessibility, and the calculators are run with real inputs.
- Type checks and lint. Money is handled as exact decimals, never floating-point, and lint blocks floating-point rounding helpers in calculation code. Results round only where the official method does (for example, EITC amounts to the dollar) and for display.
- Independent fact-check. New pages get a separate review pass against the cited sources before release, as described in our editorial standards.
Rules and data in use right now
| What | Version or period | Status |
|---|---|---|
| Federal tax rules, 2026 | us-federal-2026 v1.0.0 | Official (IRS Rev. Proc. 2025-32, Pub 15-T 2026) |
| Federal tax rules, 2027 | us-federal-2027 v0.9.1-preview | Brackets and standard deduction official (Rev. Proc. 2026-35); withholding tables are a preview until the 2027 Pub 15-T |
| Wages by occupation (BLS OEWS) | May 2025 | Released 2026-05-15 |
| Price levels by state (BEA RPP) | 2024 | Updated February 19, 2026 |
| Mortgage rate defaults (Freddie Mac PMMS) | Week of November 12, 2026 | Updated weekly |
Each calculator also shows its own calculation version next to its result, and the methodology page lists every source in detail. If a dataset passes its expected refresh date, affected pages show a notice until it's updated.
How we label estimates and projections
- Official figures come straight from the agency that sets them.
- Projected figures (for example, next year's tax brackets before the IRS announces them) are labelled as projections and replaced when the official numbers arrive.
- Estimates (paycheck results, survey figures) say what they assume, and blank inputs are listed as unknown rather than counted as $0.
Found an error?
Please tell us through the contact page, with the page, the inputs you used and what you expected. We check every report against the official source. If a published figure was wrong, we fix it, add a test that would catch it, and note material corrections on the affected page.