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