@brutoneto/core

Core library for Croatian salary calculations (bruto/neto conversions) with precise decimal arithmetic.

Installation

npm install @brutoneto/core
# or
pnpm add @brutoneto/core
# or
yarn add @brutoneto/core

Usage

Basic Gross to Net Conversion

import { grossToNet } from '@brutoneto/core'

// Simple conversion
const net = grossToNet(5000, { place: 'zagreb' })
console.log(net) // 3218

// With custom parameters
const netCustom = grossToNet(5000, {
  place: 'split',
  personalAllowanceCoefficient: 0.8,
  thirdPillarContribution: 200
})

Detailed Breakdown

import { grossToNetBreakdown } from '@brutoneto/core'

const breakdown = grossToNetBreakdown(5000, { place: 'zagreb' })
console.log(breakdown)
/*
{
  net: 3218,
  gross: 5000,
  totalCostToEmployer: 5825,
  pension: {
    firstPillar: 750,
    secondPillar: 250,
    thirdPillar: 0,
    mandatoryTotal: 1000,
    total: 1000
  },
  taxes: {
    lowerBracket: 782,
    higherBracket: 0,
    total: 782
  },
  healthInsurance: 825,
  // ... more details
}
*/

Net to Gross Conversion

import { netToGross } from '@brutoneto/core'

const gross = netToGross(3000, { place: 'zagreb' })
console.log(gross) // 4527.27

Tax Information

import { 
  getPlaceTax, 
  getPlaces, 
  getDefaultTax,
  isValidPlace 
} from '@brutoneto/core'

// Get tax rates for specific location
const zagrebTax = getPlaceTax('zagreb')
console.log(zagrebTax) // { name: 'Zagreb', taxRateLow: 0.23, taxRateHigh: 0.35 }

// Get all available places
const places = getPlaces()
console.log(places) // ['zagreb', 'split', 'rijeka', ...]

// Get default tax rates
const defaultTax = getDefaultTax()
console.log(defaultTax) // { taxRateLow: 0.2, taxRateHigh: 0.3 }

// Validate place name
console.log(isValidPlace('zagreb')) // true
console.log(isValidPlace('invalid')) // false

Configuration Options

SalaryConfig

interface SalaryConfig {
  place?: Place                          // Croatian location
  taxRateLow?: number                    // Custom low tax rate (0-0.99)
  taxRateHigh?: number                   // Custom high tax rate (0-0.99)
  personalAllowanceCoefficient?: number  // Coefficient (0.15-1.0)
  thirdPillarContribution?: number       // Monthly contribution (0-750)
}

Available Places

The library supports all Croatian cities and municipalities with their specific surtax rates:

• Major cities: zagreb, split, rijeka, osijek, zadar
• All municipalities: 556 total locations with specific tax rates
• Validation: Use isValidPlace() to check if a location is supported

Constants

import {
  HIGH_TAX_BRACKET_THRESHOLD,
  BASIC_PERSONAL_ALLOWANCE,
  MIN_PERSONAL_ALLOWANCE_COEFFICIENT,
  MAX_PERSONAL_ALLOWANCE_COEFFICIENT,
  THIRD_PILLAR_NON_TAXABLE_LIMIT
} from '@brutoneto/core'

console.log(HIGH_TAX_BRACKET_THRESHOLD) // 5000 (EUR)
console.log(BASIC_PERSONAL_ALLOWANCE)   // 600 (EUR)
console.log(THIRD_PILLAR_NON_TAXABLE_LIMIT) // 750 (EUR)

Utility Functions

Precision Utilities

import { roundEuros, percent } from '@brutoneto/core'

const rounded = roundEuros(1234.567) // 1234.57
const percentage = percent(0.23, 1000) // 230

Calculation Utilities

import {
  calcMandatoryPensionContribution,
  calcPersonalAllowance,
  calcTax,
  grossToTotal
} from '@brutoneto/core'

// Calculate pension contributions
const pension = calcMandatoryPensionContribution(5000) // 1000

// Calculate personal allowance
const allowance = calcPersonalAllowance(5000, 1.0, 'zagreb') // 600

// Calculate tax amount
const tax = calcTax(3400, 0.23, 0.35) // 782

// Calculate total employer cost
const total = grossToTotal(5000) // 5825

Tax System Overview

The Croatian tax system implemented in this library includes:

• Income Tax: Two brackets (20% up to €5,000, 30% above)
• Surtax: Location-specific rates (0-18%)
• Pension Contributions:
  • 1st pillar: 15% (mandatory)
  • 2nd pillar: 5% (mandatory)
  • 3rd pillar: up to €750/month (optional, tax-deductible)
• Health Insurance: 16.5% of gross salary
• Personal Allowance: €600 base with coefficient (0.15-1.0)

Development

# Install dependencies
pnpm install

# Run tests
pnpm test

# Build package
pnpm build

# Generate tax data
pnpm generate

# Lint code
pnpm lint

TypeScript Support

This package is written in TypeScript and includes full type definitions. All functions are strongly typed with proper interfaces for configuration objects and return values.

Precision

All calculations use Decimal.js for precise decimal arithmetic to avoid floating-point errors in financial calculations.