REGON

A .NET client library for the Polish REGON (GUS BIR1) SOAP API — query company data from the National Business Registry by NIP or KRS number.

Features

• Look up companies by NIP (tax identification number) or KRS (National Court Register number)
• Built-in dependency injection support via IServiceCollection
• Strongly-typed response model with address, legal form, activity codes (PKD), and more
• Automatic detection of legal form (sole proprietorship, LLC, joint-stock company, etc.)
• Active/suspended status resolution
• Handles the underlying SOAP/WCF communication so you don't have to

Prerequisites

• .NET 6.0 or later
• A GUS API key — register at api.stat.gov.pl/Home/RegonApi to obtain one

Installation

dotnet add package REGON

Quick Start

1. Register the client

services.AddRegonClient("<YOUR-API-KEY>");

2. Inject and use

public class CompanyService
{
    private readonly IRegonClient _regonClient;

    public CompanyService(IRegonClient regonClient)
    {
        _regonClient = regonClient;
    }

    public async Task<Company> GetCompany(string nip)
    {
        return await _regonClient.GetCompanyDataByNip(nip);
    }
}

API Reference

Methods

Method	Description
GetCompanyDataByNip(string nip)	Fetch company data by NIP (tax ID)
GetCompanyDataByKrs(string krs)	Fetch company data by KRS (court register number)

Both methods return Task<Company>.

Company Response Model

Property	Type	Description
Nip	string	Tax identification number
Krs	string	National Court Register number
Name	string	Company name
REGON	string	REGON statistical number
Street	string	Street name
BuildingNumber	string	Building number
FlatNumber	string	Flat/apartment number
City	string	City
PostCode	string	Postal code
Commune	string	Commune (gmina)
District	string	District (powiat)
Voivodeship	string	Voivodeship (province)
LegalForm	LegalForm	Legal form enum (see below)
MainPkd	string	Main PKD activity code
Pkds	List<Pkd>	All registered PKD activity codes
StartDate	DateTime	Registration date
EndDate	DateTime?	Deregistration date (null if active)
IsActive	bool	Whether the company is currently active
IsSuspended	bool	Whether the company is suspended
PhoneNumber	string	Phone number
Email	string	Email address
WebsiteUrl	string	Website URL

LegalForm Enum

Value	Name	Description
1	JDG	Sole proprietorship (jednoosobowa działalność gospodarcza)
2	SPZOO	Limited liability company (spółka z o.o.)
3	SA	Joint-stock company (spółka akcyjna)
4	SC	Civil partnership (spółka cywilna)
5	SJ	General partnership (spółka jawna)
6	SK	Limited partnership (spółka komandytowa)
7	SPZOOSK	Ltd. limited partnership (sp. z o.o. sp.k.)
8	SKA	Limited joint-stock partnership (spółka komandytowo-akcyjna)

Example Response

{
  "Nip": "7010790303",
  "Krs": "",
  "Name": "RK RECOVERY SPÓŁKA AKCYJNA",
  "Street": "Plac Konesera",
  "City": "Warszawa",
  "BuildingNumber": "10 A",
  "FlatNumber": "",
  "PostCode": "03-736",
  "REGON": "369010805",
  "Commune": "Praga-Północ",
  "District": "Warszawa",
  "Voivodeship": "MAZOWIECKIE",
  "LegalForm": 3,
  "MainPkd": "6920Z",
  "StartDate": "2017-12-15T00:00:00",
  "EndDate": null,
  "IsSuspended": false,
  "IsActive": true,
  "PhoneNumber": null,
  "Email": null,
  "WebsiteUrl": null,
  "Pkds": [
    {
      "Value": "6920Z",
      "Name": "DZIAŁALNOŚĆ RACHUNKOWO-KSIĘGOWA; DORADZTWO PODATKOWE"
    },
    {
      "Value": "6910Z",
      "Name": "DZIAŁALNOŚĆ PRAWNICZA"
    }
  ]
}

Running Tests

dotnet test

Contributing

Contributions are welcome! Here's how to get started:

1. Fork the repository
2. Create a feature branch (git checkout -b feature/my-feature)
3. Commit your changes (git commit -m 'Add my feature')
4. Push to the branch (git push origin feature/my-feature)
5. Open a Pull Request

Please make sure all existing tests pass before submitting a PR.

License

This project is licensed under the MIT License — see the LICENSE file for details.

Author

Created by Jarosław Armatys — armatys.me