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ARES API🇨🇿 ARES · enriched
ARES API: Czech business register data in one REST call
ARES is one of Europe's better open registers: free, anonymous and well documented. What it does not return is contact details, structured financials, or a full picture in a single request. CompanyData gives you 3.5 million Czech businesses with all of that, in one REST API.
150 free calls in week one · No credit card · The same API covers 200+ countries
3,505,796
Czech businesses
50+
data fields per record
CZ-NACE
official codes on every record
<200 ms
median response time
GET /api/company/search?nationalId=00177041
ŠKODA AUTO a.s.
Mladá Boleslav, Czechia
IČO00177041
Legal formAkciová společnost
CZ-NACE29100 · Motor vehicles
Employees38,200
Websiteskoda-auto.cz
Source: ARES (VR) · example200 OK · 144 ms
The basics
What is the ARES API?
Administrativní registr ekonomických subjektů is run by the Czech Ministry of Finance, and it is not a register in its own right. It is an aggregation layer that sits over the actual sources: the commercial register held by the registry courts, the trade licence register at the Ministry of Industry, and the statistical register at the Czech Statistical Office. The REST API is open, anonymous, free and CORS-enabled, which puts it ahead of most of Europe.
The friction is in the shape rather than the price. The core endpoint gives you identity and address; officers, owners and share capital live on the commercial register endpoint, the employee band lives on the statistical one, and premises live on the trade licence one, so a full picture is three or four calls per business. Contact details are not in ARES at all for ordinary businesses, and there are no structured financials anywhere: annual accounts are PDFs in the court document collection.
CompanyData starts from the same sources and flattens them. One request returns identity, address, CZ-NACE, officers, employee figures, contact details and financial signals, with the same schema in 200+ other countries.
The official API, in short
- Open and anonymous: no key, no registration, CORS enabled, free
- Aggregates the commercial, trade licence and statistical registers
- IČO must be zero-padded to 8 digits or you get an HTTP 400
- No contact details for ordinary businesses, only healthcare and schools
- Employee figures are a band, and only on the statistical endpoint
- No structured financials, accounts are PDFs in the court collection
Try it live
Look up any Czech business
Register fields plus the enrichment layer, in one response. Pick a business, no key needed for the sample.
- Official CZ-NACE codes on every record
- Officers, employees and contacts in a single call
- Same request shape in 200+ countries
Side by side
ARES API and CompanyData, per data point
ARES covers Czech registration well. CompanyData delivers 50+ enriched data points per Czech business in a single call.
| Data point | Official register | CompanyData API |
|---|---|---|
| Businesses in the file | 2,893,480 | 3,505,796 |
| Registered name and history | ✓ | ✓ |
| IČO | 1,422,765 | 3,505,720 |
| Registered address | 1,421,470 | 3,503,539 |
| CZ-NACE activity codes | ✓ | ✓ |
| Legal form and status | ✓ | ✓ |
| Officers and management | commercial register endpoint only | 2,813,296 |
| Everything in one call | ✗ | ✓ |
| Website | ✗ | 534,401 |
| Telephone number | ✗ | 342,415 |
| Mobile number | ✗ | 572,264 |
| Business email address | ✗ | 425,624 |
| Employee counts | band, statistical endpoint only | ✓ structured fields |
| Revenue and financials | PDFs in the court collection | ✓ structured fields |
| International records | ✗ | 365M+ worldwide |
Our column counts every registered entity we hold for this country, active or inactive. Some registers only serve active entities through their API, which we think is a gap: a holding or a trust can be dormant and still matter as an entity, so we keep it. Measured live in our own file, August 2026, and refreshed monthly. Register figure: economic subjects in the RES, 31 December 2025, of which 1,112,510 have no detected activity.
Access and filters
ARES is built for lookups by IČO, and its search caps at 1,000 results before returning an error, so broad selections are not enumerable. CompanyData adds segmentation on top: filter by CZ-NACE, revenue, employees, region or city, and bulk-export with enrichment included.
Price
ARES is free and stays the right tool for a registry-only lookup when you already hold the IČO. CompanyData adds the enrichment layer from €0.02 per credit, with 150 free calls in your first week and one API for 200+ countries.
See the difference
More fields than ARES returns
Contacts, employees and financials in a single request. Defaults to Czechia, switch country if you need to.
Try one:
Best practice
Working with the official ARES API
ARES is genuinely good, and you can call it in a minute. Here is how, and the six things that cost teams the most time, whether you enrich with us or not.
1
Nothing to register
No key and no account. The developer information and the OpenAPI specification are at ares.gov.cz, and the endpoints answer anonymous requests.
2
Zero-pad the IČO to 8 digits
Seven digits returns HTTP 400, not an empty result. If your storage typed IČO as an integer, the leading zero is already gone.
3
Read seznamRegistraci first
The core response flags which sub-registers hold data for that business, so you can skip the follow-up calls that would come back empty.
Honestly: ARES is a well-built free API and the right choice for registry-only lookups by IČO. If you need contact details, employee figures, financials, or all of it in one call across 200+ countries, that is us.
Get your API key01
Zero-pad every IČO
The IČO is exactly eight digits and it is hard-enforced. Seven digits gives you HTTP 400 with a format error, so a 400 tells you the formatting is wrong and a 404 tells you the business is not there.
02
The legacy XML API is gone, not deprecated
wwwinfo.mfcr.cz no longer resolves at all. Parallel operation ended in January 2024, so old integrations fail at DNS resolution, which surfaces as a connection error rather than an HTTP status and hides behind broad retry logic.
03
Budget three to four calls per business
Officers, owners and capital are on the commercial register endpoint, the employee band and principal activity on the statistical one, premises on the trade licence one. Only the core identity fields come from one call.
04
The commercial register returns full history
Officers, shareholders and capital arrive as arrays of every version ever registered. Filter on the absent deletion date or you will show a director who left years ago.
05
Amounts use a semicolon as the decimal separator
Share capital comes back as a string like 16708850000;00. No standard number parser handles that, so you have to normalise it yourself. Dates, by contrast, are clean ISO.
06
CZ-NACE changed in January 2026
The main field now carries CZ-NACE 2025 and a second field holds the old scheme. Before 2026 both were identical, so any mapping built earlier silently reads the wrong one.
Use cases
What teams build on Czech register data
KYB and onboarding
Verify Czech counterparties by IČO. Check legal form, status and management automatically during signup.
Lead generation
Build prospect lists filtered by CZ-NACE code, region, revenue or business size.
CRM enrichment
Append IČO, DIČ, CZ-NACE codes, financials and contacts to your Czech accounts in bulk.
Risk and compliance
Monitor insolvencies, liquidations and officer changes across your Czech supplier base.
Form autocomplete
Type-ahead on registered names in signup forms, so the IČO and address arrive zero-padded and spelled the way the register spells them.
ERP and finance systems
Match suppliers and customers to an IČO once, then keep names, status and addresses in sync automatically.
Beyond Czechia
Czechia is one of 200+ countries on the same API
Same request shape, same response schema, from ARES to Companies House, the KVK and Sirene. Build the Czech integration once and take it across the border.
Explore the Company Data API
More local registers
The same API, register by register
Customer stories
What teams do with register data
Onboarding, KYB and supplier checks in production, on the same search and export calls you just tried.
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Live business KYC inside BankID
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Cellbunq · KYB
Global KYB compliance on one integration
Up-to-date business details from around the world, screened straight inside the onboarding flow.
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Zen.com · Fintech
Customer onboarding without the friction
Large-scale KYB verification through business lookup, built straight into the signup path.
Read the story
Sumsub · KYB platform
Verifying the address and the director, at scale
350M statutory addresses and registry director records inside Sumsub's global KYB flows, so shell offices and nominee directors get caught at onboarding.
Read the story
Veriff · Identity verification
UBO checks where the paperwork is hardest
Registry-sourced business and UBO data across Africa, Asia and Latin America, with 80% fewer manual reviews.
Read the storyARES API Pricing
Transparent, credit-based pricing. Start with a free trial.
Free trial
Verify your first 150 Czech businesses free
- 150 lookups and 10 exports in week one, key issued instantly
- 1 credit per business looked up, usage-based after that
- No card, no contract, no sales call
Questions? Ask a human.
No ticket queue. Your question lands with our data team and you get an answer within 24 hours.
Amsterdam HQVijzelgracht 53D · +31 20 705 2360
BerlinFriedrichstraße 123 · +49 30 21480480
DubaiBuilding A1, Dubai Digital Park, Dubai Silicon Oasis
Mon to Fri 9:00 to 17:30 CET · info@companydata.com
What our customers say
Real feedback from the people using CompanyData every day.
★★★★★
The best data company we have worked with.
Helmut Huberti, M.D.
World Arthrosis Org., Heidelberg
★★★★★
Great feedback from our team on the data quality.
Stefania Guerra
Dyson, Milan
Frequently asked questions
Is the ARES API free?
Yes. ARES is open and anonymous: no key, no registration, CORS enabled, published under Czech open-data obligations. The Ministry of Finance may restrict users sending more than 500 queries a minute, and search results cap at 1,000 rows.
Why does my ARES lookup return HTTP 400?
Almost always because the IČO is not zero-padded. It must be exactly eight digits, so 6947 has to be sent as 00006947. If your storage typed the IČO as an integer, the leading zeros were stripped on import and every such lookup fails.
A 400 means the format is wrong. A 404 means the format was fine but the business is not there.
Does the ARES API return contact details?
Not for ordinary businesses. A contact object exists only in the healthcare provider and school registers, two narrow verticals. There is no phone, email or website for a normal Czech business anywhere in ARES.
We supply telephone, mobile, email and website on the records where they are available.
Can I get employee counts from ARES?
Only as a band, and only from the statistical register endpoint. The values run from no employees through to 10,000 and more, and the not-stated code is very common for smaller businesses. We carry employee figures as structured fields you can filter and sort on.
Are Czech financial statements available through ARES?
No. There is no revenue, assets or profit figure anywhere in ARES. The only monetary values are registered share capital and deposits. Actual accounts sit in the court document collection as PDFs, outside ARES, which gives you only the file reference to find them with.
What happened to the old ARES XML API?
It is gone rather than deprecated. Parallel operation ended on 1 January 2024 and the old host no longer resolves, so legacy code fails at DNS resolution instead of returning an HTTP error. The current API is REST and JSON with entirely different field names.
How many Czech businesses do you cover?
3.5 million Czech registrations, including sole traders and branches, updated continuously from the register and other official sources.
Make 150 Free API Calls Before You Spend Anything
Tell us which Czech businesses you need. You get a trial key with 150 lookups and 10 exports, plus a real sample response for your target market, within 24 hours.
or call +31 (0)20 705 2360