Use our tax API to create a gross to net calculator

Tuesday, January 19, 2021

3 minute read

As part of our tax technology offering, Aeco publicly opens its Tax API. The Tax API can be used to make various calculations and optimisations based on tax legislation. In this blogpost, we cover a gross to net calculator for Belgian self-employed individuals. The Tax API is part of the tax technology offering developed by Aeco to provide programatic access to tax legislation. With this Tax API we aim to disrupt the way companies, governments and universities interact with tax regulations.

When to use

This route enables you to perform basic tax calculations for Belgian self-employed persons. Basic tax calculations include a calculation from gross revenue to net income.

Example: An example of an application that works on this route can be found here (dutch only).

Tax technology - Gross to net calculation

For a simple gross to net calculation we suggest using the following steps.

Step 1: Determine if the calculation is for a director or a one man business.

The tax treatment of both is very similar but the fixed costs (if applicable) are calculated with a different percentage. Please note that a combination of the two is also plausible but not very common.

Step 2 (optional): Add other information more specific about the user such as:

  • number_of_dependent_persons
  • real_estate_net_taxable_income
  • self_employed_type
  • employee_net_taxable_income

Step 3: Use the output

You can use a combination of the returned parameters to provide information to your user. The most relevant parameters are:

  • self_employed_social_security_contribution
  • personal_income_tax
  • yearly_net_income

Additional information

  • an average municipal tax of 7% is used
  • a social security administration cost of 3.05% is used
  • the social security contribution is calculated to reflect the final contribution in a given year following the rates applicable by the law for the income year
  • the personal income tax is calculated following the rates applicable by the law for the income year

Get started with the tax API

Do you want to create your own tax technology tool? Get started with the Tax API and request a Tax API Key or look at the Tax API documentation.

Tax API Key: In order to use this API you need an API-key. A key can be requested by contacting us at After you obtained an API key you can start sending requests by including the x-api-key: YOUR_API_KEY into the header of your request.

Tax API Documentation: Are you curious to find out more about the future of tax and tax technology? Then it's your lucky day since the Tax API documentation is publicly available.

To see our API in action, have a look at the Quickstart! is a service by Aeco

Aeco is a family-owned business founded by three brothers with a complementary skill-set.

We are a Legal Tech company transforming the legal industry. We believe that legal services can be performed differently to bring top-quality advice at an affordable price..