Federal capital-gains tax: long-term stacked across the 2026 0%/15%/20% breakpoints, short-term at ordinary marginal rates, plus the 3.8% Net Investment Income Tax.

Quarterly estimated-tax safe harbor (Form 1040-ES): the required annual payment and per-quarter amount to avoid an underpayment penalty.

Federal income tax on ordinary income for 2026: AGI from gross minus above-the-line adjustments, standard or itemized deduction, the 2026 brackets, and a flat nonrefundable credit amount. Distinct from /v1/paycheck (which nets FICA + state per pay period).

FLSA overtime pay: regular and overtime hours, the overtime rate, and gross pay for a week — federal 1.5× over 40 hours by default, any threshold/multiplier configurable.

Self-employment (SE) tax on Schedule C net profit — Social Security to the 2026 $184,500 wage base, Medicare, Additional Medicare, and the deductible half.

Standalone 2026 state income tax for any of 51 US jurisdictions — progressive/flat/no-tax schedules, MFJ doubling — applied to the income you provide.