taxer

universal tax calculator javascript library to calculate all kinds of taxes through out the world.

Library Architecture

It's designed with plugin mechanism and minimalist in mind. By default:

const taxer = new Taxer();
taxer.use(new CustomCalctor());
const taxInfo = taxer.calc(countryCode, income, options);

in which:

CustomCalctor should be a class implements Calctor interface which has:

• isMatched(countryCode, taxableIncome, options) method: to be hooked up if it is the first to return true.
• calc(taxableIncome, options) method: the taxInfo is calculated and returned.

If no matched calculator, an error will be thrown.

For example:

export default class VnCalctor {
  constructor() {
  }

  calc(taxableIncome, options={}) {
    return {
      taxableIncome: taxableIncome
    }
  }

  isMatched(countryCode, income, options) {
    if (typeof countryCode === 'string') {
      countryCode = countryCode.toLowerCase();
    }
    return ['vn', 'vnm', 704, 'vietnam', 'viet nam'].indexOf(countryCode) > -1;
  }

  // required by exector under the hood, usually ignored by calctors
  exec() {
    return undefined;
  }
}

For easier implementation, we should extend the base class Calctor, as the following:

import { Calctor } from 'taxer';


export default class VnCalctor extends Calctor {
  get currency() {
    return 'VND';
  }

  get supportedCountryCodes() {
    return ['vn', 'vnm', 704, 'vietnam', 'viet nam'];
  }

  doMonthlyGrossPayrollCalc(income, options) {
    return monthlyPayrollProgressiveCalctor.calc(income, options);
  }

  doYearlyGrossPayrollCalc(income, options) {
    return yearlyPayrollProgressiveCalctor.calc(income, options);
  }

  doMonthlyNetPayrollCalc(income, options) {
    return monthlyPayrollProgressiveCalctor.calc(income, options);
  }

  doYearlyNetPayrollCalc(income, options) {
    return yearlyPayrollProgressiveCalctor.calc(income, options);
  }
}

That's how the library architecture works.

How to use

1. Configure

1.1. From the default taxer with built-in tax calculators:

const taxer = defaultTaxer();
// add more custom calculator
taxer.use(new CustomCalctor(options));

1.2. From scratch

const taxer = new Taxer();
taxer.use(VnCalctor());
taxer.use(UsaCalctor());
taxer.use(SgCalctor());
taxer.use(CustomCalctor(options));

2. Use

const taxInfo = taxer.calc(countryCode, income, options);
console.log(taxInfo);

How to develop

This is the minimalist plugin architecture inspired by express.js and koa.js a lot. Let's keep it as minimal and lightweight as possible.

Clone this repository and:

$ npm install
$ npm run test

Or with Docker:

$ docker-compose up

How to contribute

By writing custom tax plugins to create a good solid universal tax system throughout the world.

Follow Teracy workflow: http://dev.teracy.org/docs/workflow.html

References

These are related similar projects we should take a look:

• https://github.com/rkh/income-tax

• https://www.npmjs.com/package/uk-income-tax

License

MIT license. See LICENSE file.