# US Tax Calculators

Federal income tax, FICA, capital gains, deduction and retirement-limit estimates from IRS published figures.

## How to pay

Machine-payable over x402. USDC on: Base (eip155:8453), Solana (solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp), Polygon (eip155:137), Arbitrum One (eip155:42161).
No accounts. No API keys. No signup. The paying wallet is the account.

## Machine-readable

- OpenAPI: https://us-tax-calc.x402tookit.com/openapi.json
- x402 manifest: https://us-tax-calc.x402tookit.com/.well-known/x402
- Catalog (free): https://us-tax-calc.x402tookit.com/catalog
- Health (free): https://us-tax-calc.x402tookit.com/health
- Uptime (free): https://us-tax-calc.x402tookit.com/uptime

## Endpoints (8)

### GET /bracket-lookup — $0.02
Which US federal income tax bracket a taxable income falls in: marginal rate, bracket edges and dollars to the next bracket.
Params: taxable_income: number, filing_status: string, year?: integer
Example: https://us-tax-calc.x402tookit.com/bracket-lookup?taxable_income=100000&filing_status=single&year=2024

### GET /capital-gains-tax — $0.03
US long-term capital gains tax: 0/15/20 percent stacked on ordinary taxable income, plus 3.8 percent net investment income tax.
Params: filing_status: string, ordinary_taxable_income: number, long_term_gains: number, magi?: number, net_investment_income?: number, year?: integer
Example: https://us-tax-calc.x402tookit.com/capital-gains-tax?filing_status=single&ordinary_taxable_income=80000&long_term_gains=50000&year=2025

### GET /income-tax-estimate — $0.03
US federal income tax estimate by filing status and year, with bracket breakdown and marginal and effective rates.
Params: filing_status: string, income: number, year?: integer, adjustments?: number, itemized_deductions?: number, salt_paid?: number, aged_count?: integer, blind_count?: integer
Example: https://us-tax-calc.x402tookit.com/income-tax-estimate?filing_status=single&income=120000&year=2025

### GET /payroll-tax — $0.03
US FICA tax on wages (Social Security, Medicare, Additional Medicare) with the employer split, and self-employment tax.
Params: wages?: number, self_employment_income?: number, filing_status?: string, year?: integer
Example: https://us-tax-calc.x402tookit.com/payroll-tax?wages=90000&year=2025

### GET /retirement-limits — $0.02
IRS retirement and HSA contribution limits by year: 401(k), IRA, catch-up, SIMPLE, HSA, with an age-adjusted personal limit.
Params: year?: integer, age?: integer
Example: https://us-tax-calc.x402tookit.com/retirement-limits?year=2026&age=52

### GET /standard-deduction — $0.02
US federal standard deduction by filing status and tax year, with age 65 or blind add-ons and the dependent filer limit.
Params: filing_status: string, year?: integer, aged_count?: integer, blind_count?: integer, dependent?: boolean, earned_income?: number
Example: https://us-tax-calc.x402tookit.com/standard-deduction?filing_status=single&year=2025&aged_count=1

### GET /tax-years — $0.02
Which US tax years and IRS figures this shelf bundles, with source documents, data date and a staleness warning.
Params: year?: integer
Example: https://us-tax-calc.x402tookit.com/tax-years?year=2026

### GET /withholding-estimate — $0.03
Annual and per-paycheck take-home from salary: federal withholding (IRS percentage method) plus FICA. State tax not included.
Params: salary: number, filing_status: string, pay_periods?: integer, pretax_retirement?: number, pretax_benefits?: number, year?: integer
Example: https://us-tax-calc.x402tookit.com/withholding-estimate?salary=85000&filing_status=single&pay_periods=26&year=2026

## Terms

Federal-only educational estimates from IRS published figures for the bundled tax years. Not tax advice; ignores credits, AMT, state tax and many deductions. Figures must be refreshed every year.