spanish-tax-calculators

Pure JavaScript calculators for Spanish taxes — no dependencies, no UI.

Demo

calculators.dslab.fyi

Install

npm install spanish-tax-calculators

Usage

import {
  calculateAutonomo,
  calculateJointTax,
  optimizeCollaboratorSalary,
  calculateItpAmount,
} from 'spanish-tax-calculators'

// Autónomo tax breakdown
const result = calculateAutonomo({
  annualNetRevenue: 50000,
  autonomoType: 'individual',
  region: 'madrid',
  year: 2026,
})
console.log(result.netTakeHome) // → 33495.38

// Autónomo + Colaborador joint optimization
const optimized = optimizeCollaboratorSalary({
  userNetIncome: 50000,
  region: 'madrid',
  autonomoType: 'individual',
})
console.log(optimized.optimalMonthly) // → 1000

// ITP property transfer tax
const itp = calculateItpAmount(300000, {
  itp_brackets: [
    { upTo: 400000, rate: 8.0 },
    { upTo: 600000, rate: 9.0 },
    { upTo: null, rate: 10.0 },
  ],
})
console.log(itp) // → 24000

API Reference

Autónomo

| Function | Description | |---|---| | calculateAutonomo(params) | Full autónomo tax breakdown: SS, IRPF, net take-home | | calcGeneralExpenses(revenue, type) | General expenses deduction (7% individual, 3% director, max €2,000) | | calcPersonalMinimum({ age, children, disability }) | Personal minimum allowance (mínimo personal y familiar) |

IRPF

| Function | Description | |---|---| | calcProgressiveTax(base, brackets) | Progressive tax from any bracket table | | calcProgressiveTaxWithBreakdown(base, brackets) | Same, with per-bracket breakdown | | calcIrpfState(base) | State IRPF component | | calcIrpfRegional(base, region) | Regional IRPF for 19 comunidades autónomas | | IRPF_REGIONAL_BRACKETS | All regional bracket tables |

Social Security

| Function | Description | |---|---| | findSSBracket(monthlyIncome) | Find SS bracket (1–15 tramos) | | findSSQuota(monthlyIncome, year, timeAsAutonomo) | Monthly SS quota (with tarifa plana support) | | findSSQuotaForCollaborator(monthlyIncome, year) | RETA quota for autónomo colaborador |

Autónomo Colaborador

| Function | Description | |---|---| | calculateCollaboratorSide(params) | Collaborator tax breakdown | | calculateJointTax(params) | Combined autonomo + collaborator picture | | optimizeCollaboratorSalary(params) | Find optimal collaborator salary to minimize tax | | calcWorkIncomeReduction(rendimientoNeto) | Reducción por rendimientos del trabajo (Art. 20 LIRPF) |

ITP (Property Transfer Tax)

| Function | Description | |---|---| | calculateItpAmount(price, region) | ITP with progressive brackets or flat rate fallback |

Data

Regional tax data (ITP, AJD, IGIC rates) is available via the JSON file at src/data/spain-tax-data.json.

License

MIT