How the USA self-employed (federal) calculator is verified

Inputs

Input	Field	Type
Annual net business earnings (USD)	`netEarnings`	number

The formula

Each derived value below is computed by the Valem engine from the expression shown, in this order. Nothing else runs — there is no hidden code path.

Derived value	Field	Formula (JSONata)
Se Tax Base	`seTaxBase`	`$round(netEarnings * $const.seBase, 2)`
Self-employment tax	`selfEmploymentTax`	`$round($const.ssRate * $min([seTaxBase, $const.ssWageBase]) + $const.medicareRate * seTaxBase, 2)`
QBI deduction (20%)	`qbiDeduction`	`$round($const.qbiRate * $max([0, netEarnings - selfEmploymentTax / 2]), 2)`
Taxable Income	`taxableIncome`	`$round($max([0, netEarnings - selfEmploymentTax / 2 - qbiDeduction - $const.standardDeduction]), 2)`
Federal income tax	`federalIncomeTax`	`($t := taxableIncome; $round($const.r1 * $min([$t, $const.b1]) + $const.r2 * $max([0, $min([$t, $const.b2]) - $const.b1]) + $const.r3 * $max([0, $min([$t, $const.b3]) - $const.b2]) + $const.r4 * $max([0, $min([$t, $const.b4]) - $const.b3]) + $const.r5 * $max([0, $min([$t, $const.b5]) - $const.b4]) + $const.r6 * $max([0, $min([$t, $const.b6]) - $const.b5]) + $const.r7 * $max([0, $t - $const.b6]), 2))`
Net income / year (federal only)	`netIncome`	`$round($max([0, netEarnings - selfEmploymentTax - federalIncomeTax]), 2)`

Rates and thresholds

The expressions above read these as $const. They are the figures the annual refresh replaces, so they live as data rather than being written into the formulas — which is what makes a year-on-year change a one-line diff instead of an edit to arithmetic.

Constant	Value
`seBase`	0.9235
`ssRate`	0.124
`medicareRate`	0.029
`ssWageBase`	184500
`qbiRate`	0.2
`standardDeduction`	16100
`b1`	12400
`b2`	50400
`b3`	105700
`b4`	201775
`b5`	256225
`b6`	640600
`r1`	0.1
`r2`	0.12
`r3`	0.22
`r4`	0.24
`r5`	0.32
`r6`	0.35
`r7`	0.37

Test vectors (3)

Every case is executed against this model on each build, by the Java engine and independently by a JavaScript one. A mismatch of a single cent fails the build, so the page cannot ship advertising a figure the model no longer produces.

Case 1 — 100,000 USD net earnings — a typical full-time contractor

given `netEarnings`	100000
expect `seTaxBase`	92350
expect `selfEmploymentTax`	14129.55
expect `qbiDeduction`	18587.05
expect `taxableIncome`	58248.18
expect `federalIncomeTax`	7526.6
expect `netIncome`	78343.85

Case 2 — 40,000 USD — part-time

given `netEarnings`	40000
expect `seTaxBase`	36940
expect `selfEmploymentTax`	5651.82
expect `qbiDeduction`	7434.82
expect `taxableIncome`	13639.27
expect `federalIncomeTax`	1388.71
expect `netIncome`	32959.47

Case 3 — 250,000 USD — above the Social Security wage base

given `netEarnings`	250000
expect `seTaxBase`	230875
expect `selfEmploymentTax`	29573.38
expect `qbiDeduction`	47042.66
expect `taxableIncome`	172070.65
expect `federalIncomeTax`	33894.96
expect `netIncome`	186531.66

Sources

IRS — Self-employment tax (Social Security and Medicare taxes) · checked 2026-08-22
2026 federal income tax brackets and standard deduction (Rev. Proc. 2025-32) · checked 2026-08-22

Check it yourself — and reuse it

The whole model as JSON — inputs, outputs, formulas, vectors and sources in one re-runnable document.

This model is published under CC BY 4.0: use it, adapt it, build on it, with attribution. The licence covers the model — the expression of each rule and the arrangement of the catalog. The rates and thresholds are law, and nobody licenses those; the sources above are where they come from.

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