Documentation of the register API

Every endpoint with method, path, parameters, request, an example answer for RELACON GmbH, the fields of the answer and the error codes. Amounts appear in the examples only as placeholders.

Contents

Access and authentication

Create the key while signed in, in your account under API and MCP. It starts with fbd_ and is shown once. Every call carries it in the Authorization header as Bearer.

Authorization: Bearer fbd_…

Allowance per UTC month: Free 50, Pro 50, Business 1,000 calls. Every request costs one call, search, customer check and every PDF included. No fee per query.
Every answer carries x-ratelimit-limit, x-ratelimit-remaining and x-ratelimit-reset. When the calls are used up, the API answers 429 and names limit and resetAt in the body.
When a subscription ends, the same key keeps working with the limits of Free.
There is no separate sandbox: the free key runs on the live data.

Base address: https://api.firmenbuchdaten.at/v1

The previous address https://firmenbuchdaten.at/api/v1 stays valid and gives the same answers. https://api.firmenbuchdaten.at serves the API only, no pages.

Company API

Finds a company by name and returns its register data: name, seat, legal form, status, the filed annual accounts and edicts in insolvency proceedings. For setting up a new customer or supplier.

GET `/v1/companies`

Search companies by name. Hits from our index, without a register call, with the filters of the advanced search. At least q or one filter. One page is one call. Other filters (state, district, ÖNACE) answer 400 unsupported_filter.

Still valid: https://firmenbuchdaten.at/api/v1/companies

Plan: All plans

Parameters

Name	Type	Required	Description
`q`	string, query	no	Name, part of it (at least three characters) or register number
`rechtsform`	string, query	no	Legal form as in the register, e.g. Gesellschaft mit beschränkter Haftung
`sitz`	string, query	no	Seat as in the register, e.g. Wien
`gkl`	string, query	no	Size class of the latest accounts: W, K, M or G
`seit`	string, query	no	Only companies with accounts filed on or after this day (YYYY-MM-DD)
`limit`	integer, query	no	Hits per page, 1 to 50, default 25
`cursor`	string, query	no	nextCursor of the previous answer; at most 20 pages

Request

curl -H "Authorization: Bearer fbd_…" \
  "https://api.firmenbuchdaten.at/v1/companies?q=relacon"

Response

{
  "results": [
    {
      "fnr": "508415w",
      "name": "RELACON GmbH",
      "sitz": "Klosterneuburg",
      "rechtsform": "Gesellschaft mit beschränkter Haftung",
      "status": "eingetragen"
    }
  ],
  "nextCursor": null
}

Field	Type	Description
`results`	array	Hits of the page
`results[].fnr`	string	Register number with check letter
`results[].name`	string	Company name
`results[].sitz`	string	Seat according to the register
`results[].rechtsform`	string	Legal form
`results[].status`	string	eingetragen (registered) or gelöscht (deleted)
`nextCursor`	string \| null	Value for cursor of the next page, null at the end

Errors

Status	Code	Meaning
400	`query_too_short`	No term and no filter, or a term shorter than three characters.
400	`unsupported_filter`	A parameter the search does not know; the answer names the supported ones.
400	`cursor_too_deep`	More than 20 pages; narrow the filters.

GET `/v1/companies/{fnr}`

Company data. Name, seat, legal form, status, the list of annual accounts with balance sheet date, size class and filing date, the latest entry date and edicts on sales and leases in insolvency proceedings. No management, no shareholders; an edict names the administrator as the edict file publishes it.

Still valid: https://firmenbuchdaten.at/api/v1/companies/{fnr}

Plan: All plans. Business also: industry (ÖNACE) according to Statistics Austria, public contracts, FMA sanctions, credit institution according to OeNB and the number of connections.

Parameters

Name	Type	Required	Description
`fnr`	string, path	yes	Register number with check letter, e.g. 508415w

Request

curl -H "Authorization: Bearer fbd_…" \
  "https://api.firmenbuchdaten.at/v1/companies/508415w"

Response

{
  "fnr": "508415w",
  "name": "RELACON GmbH",
  "sitz": "Klosterneuburg",
  "rechtsform": "Gesellschaft mit beschränkter Haftung",
  "status": "eingetragen",
  "soleTrader": false,
  "annualAccounts": [
    {
      "stichtag": "2025-12-31",
      "sizeClass": "W",
      "filed": "2026-01-21",
      "formats": [
        "pdf",
        "xml"
      ]
    },
    {
      "stichtag": "2024-12-31",
      "sizeClass": "W",
      "filed": "2025-05-03",
      "formats": [
        "pdf",
        "xml"
      ]
    }
  ],
  "lastChange": null,
  "insolvencyNotices": [],
  "retrievedAt": "2026-10-29T07:49:23.526Z",
  "source": "Österreichisches Firmenbuch, Republik Österreich, vertreten durch das BMJ, offene Daten unter CC BY 4.0"
}

Field	Type	Description
`fnr`	string	Register number with check letter
`name`	string	Company name
`sitz`	string	Seat according to the register
`rechtsform`	string	Legal form
`status`	string	Status, e.g. eingetragen (registered) or gelöscht (deleted)
`soleTrader`	boolean	true for sole traders, whose name is a person's name
`annualAccounts[]`	array	Filed annual accounts: stichtag, sizeClass, filed, formats
`lastChange`	string \| null	Latest entry date from the register's change feed
`insolvencyNotices[]`	array	Edicts: published, court, caseNo, kind, transaction, description, administrator
`retrievedAt`	string	Time of the last register request (ISO 8601)
`source`	string	Source line, show it with the data
`lei[]`	array	LEI according to GLEIF; empty until the GLEIF data is loadedBusiness only
`oenace`	object \| null	Industry by ÖNACE according to Statistics AustriaBusiness only
`publicAwards`	object \| null	Public contracts according to data.gv.atBusiness only
`fmaSanctions[]`	array	FMA sanctions against the company: title, date, urlBusiness only
`bank`	object \| null	Credit institution according to OeNBBusiness only
`network`	object \| null	Connections: persons (natural persons with functions in other active companies) and companies (number of those companies), counts onlyBusiness only
`persons`	string	Path to the functions of this company (person API)Business only

Errors

Status	Code	Meaning
400	`invalid_fnr`	Not a valid register number, for example a wrong check letter.
404	`not_found`	No such register number.

GET `/v1/companies/{fnr}/gewerbe`

Trade licences (GISA). Trade licences of a company from the Austrian trade information system: wording, trade code, location, status (active, dormant, ended), start and end. One single query per call through the public GISA interface, cached for 7 days, matched by register number only. No managers, no lists, not for sole traders.

Still valid: https://firmenbuchdaten.at/api/v1/companies/{fnr}/gewerbe

Plan: Pro and Business.

Parameters

Name	Type	Required	Description
`fnr`	string, path	yes	Register number with check letter, e.g. 508415w

Request

curl -H "Authorization: Bearer fbd_…" \
  "https://api.firmenbuchdaten.at/v1/companies/508415w/gewerbe"

Response

{
  "fnr": "508415w",
  "fetchedAt": "<JJJJ-MM-TTThh:mm:ssZ>",
  "trades": [
    {
      "gisaZahl": "<GISA-Zahl>",
      "wortlaut": "<Wortlaut>",
      "gewerbeschluessel": "<Schlüssel>",
      "plz": "<PLZ>",
      "ort": "<Ort>",
      "status": "aktiv",
      "beginn": "<JJJJ-MM-TT>",
      "ende": null
    }
  ],
  "source": "Austrian trade information system (GISA), Federal Ministry of Economy, Energy and Tourism, single query through the public interface"
}

Field	Type	Description
`fnr`	string	Register number
`fetchedAt`	string	Time of the GISA query
`trades[]`	array	gisaZahl, wortlaut, gewerbeschluessel, plz, ort, status, beginn, ende
`source`	string	Source line

Errors

Status	Code	Meaning
400	`invalid_fnr`	Not a valid register number.
403	`plan`	Pro or Business only.
404	`unknown_company`	The company is not in our database yet. Fetch the company first, then GISA.
404	`sole_trader`	No GISA lookup for sole traders.
429	`account_limit`	This account's daily limit of GISA lookups is reached.
429	`in_progress`	This company is being looked up; in a minute the result is in the cache.
503	`paused`	GISA lookups are paused (minute or day budget, or GISA does not answer).

Annual accounts API

Returns a year's balance sheet and P&L as the company filed them, with our ratios, and the annual accounts as PDF. For in-house credit checks, files and reports.

GET `/v1/companies/{fnr}/financials`

Balance sheet, P&L and ratios. Per year the balance sheet items and, where filed, the P&L in cents, unchanged from the register, plus our ratios. load=1 fetches one missing year from the register.

Still valid: https://firmenbuchdaten.at/api/v1/companies/{fnr}/financials

Plan: Pro and Business: every company. Free: only the company of your free query.

Parameters

Name	Type	Required	Description
`fnr`	string, path	yes	Register number with check letter, e.g. 508415w
`load`	integer, query	no	1 = fetch one missing year

Request

curl -H "Authorization: Bearer fbd_…" \
  "https://api.firmenbuchdaten.at/v1/companies/508415w/financials?load=1"

Response

{
  "fnr": "508415w",
  "name": "RELACON GmbH",
  "years": [
    {
      "stichtag": "2025-12-31",
      "sizeClass": "W",
      "hasProfitAndLoss": false,
      "positionsCents": {
        "<Posten>": "<Betrag in Cent>"
      },
      "evaluation": {
        "<Kennzahl>": "<Wert>"
      }
    }
  ],
  "notLoaded": [],
  "note": "positionsCents: register figures in euro cents, unchanged. evaluation: computed by firmenbuchdaten.at, not part of the register.",
  "source": "Österreichisches Firmenbuch, Republik Österreich, vertreten durch das BMJ, offene Daten unter CC BY 4.0"
}

Field	Type	Description
`fnr`	string	Register number
`name`	string	Company name
`years[]`	array	Per loaded year: stichtag, sizeClass, hasProfitAndLoss, positionsCents, evaluation
`years[].positionsCents`	object	Register items in euro cents, unchanged
`years[].evaluation`	object	Ratios computed by firmenbuchdaten.at, not part of the register
`notLoaded[]`	array	Balance sheet dates not loaded yet (load=1 fetches one)
`note`	string	Note on which figures come from the register and which from us
`source`	string	Source line

Errors

Status	Code	Meaning
403	`plan_without_financials`	Free: figures only for the company of your free query. Pro or Business for every company.
404	`not_found`	No such register number.

GET `/v1/companies/{fnr}/documents/{stichtag}`

Annual accounts as PDF. The annual accounts as filed with the register. At most 20 PDFs per key and hour.

Still valid: https://firmenbuchdaten.at/api/v1/companies/{fnr}/documents/{stichtag}

Plan: Pro and Business.

Parameters

Name	Type	Required	Description
`fnr`	string, path	yes	Register number with check letter, e.g. 508415w
`stichtag`	string, path	yes	Balance sheet date as YYYY-MM-DD

Request

curl -H "Authorization: Bearer fbd_…" \
  "https://api.firmenbuchdaten.at/v1/companies/508415w/documents/2025-12-31" \
  -o abschluss.pdf

Response

The PDF file (application/pdf) as filed with the register.

Errors

Status	Code	Meaning
400	`invalid`	Register number or date invalid.
403	`plan_without_financials`	PDFs come with Pro or Business.
429	`rate`	More than 20 PDFs in one hour.

Person API

Shows who holds management, authorised signatory or another function in a company according to the register, and in which other companies the same person is entered. For checking business partners, Business only. Every call is logged for 90 days.

GET `/v1/persons`

Search persons. Persons with functions in the register by name, at most 20 hits with name and number of companies. With geburtsdatum exactly the one person with this name and birth date. We do not store or return the birth date itself.

Still valid: https://firmenbuchdaten.at/api/v1/persons

Plan: Business.

Parameters

Name	Type	Required	Description
`name`	string, query	yes	Name or part of it
`geburtsdatum`	string, query	no	Birth date YYYY-MM-DD, for an exact hit

Request

curl -H "Authorization: Bearer fbd_…" \
  "https://api.firmenbuchdaten.at/v1/persons?name=<Name>"

Response

{
  "results": [
    {
      "key": "<key>",
      "name": "<Name>",
      "companies": 2,
      "legalEntity": false
    }
  ],
  "source": "Österreichisches Firmenbuch, Republik Österreich, vertreten durch das BMJ, offene Daten unter CC BY 4.0"
}

Field	Type	Description
`results[].key`	string	Key for /v1/persons/{key}
`results[].name`	string	Name as in the register
`results[].companies`	integer	Number of companies with a function
`results[].legalEntity`	boolean	true for legal entities (e.g. a GmbH as shareholder)
`source`	string	Source line

Errors

Status	Code	Meaning
400	`name_too_short`	No part of the name with at least three characters.
403	`plan_without_persons`	Persons through the API come with Business only.
429	`person_rate`	More than 30 person calls in an hour or 100 in a day (shared with the person search of the website).

GET `/v1/persons/{key}`

Functions of a person. Current functions with company, register number, function and since when, plus functions no longer in the register extract, with the day we noticed.

Still valid: https://firmenbuchdaten.at/api/v1/persons/{key}

Plan: Business.

Parameters

Name	Type	Required	Description
`key`	string, path	yes	Key of the person from a search (24 characters)

Request

curl -H "Authorization: Bearer fbd_…" \
  "https://api.firmenbuchdaten.at/v1/persons/<key>"

Response

{
  "key": "<key>",
  "name": "<Name>",
  "legalEntity": false,
  "functions": [
    {
      "fnr": "508415w",
      "company": "RELACON GmbH",
      "sitz": "Klosterneuburg",
      "companyStatus": "eingetragen",
      "code": "GF",
      "function": "<Funktion>",
      "since": "<JJJJ-MM-TT>",
      "representation": "<Vertretung>"
    }
  ],
  "endedFunctions": [],
  "source": "Österreichisches Firmenbuch, Republik Österreich, vertreten durch das BMJ, offene Daten unter CC BY 4.0"
}

Field	Type	Description
`key`	string	Key of the person
`name`	string	Name as in the register
`legalEntity`	boolean	true for legal entities
`functions[]`	array	fnr, company, sitz, companyStatus, code, function, since, representation
`endedFunctions[]`	array	fnr, company, code, function, since, notInExtractSince (day the function was no longer in the extract)
`source`	string	Source line

Errors

Status	Code	Meaning
400	`invalid_key`	Not a valid key.
403	`plan_without_persons`	Persons through the API come with Business only.
404	`not_found`	No person with this key.
429	`person_rate`	Hourly or daily limit of person calls reached.

GET `/v1/companies/{fnr}/persons`

Functions in a company. Who holds a function in this company (management, authorised signatory, shareholders as in the extract, supervisory board), since when and how they represent it, and who is no longer in the extract. We do not keep shareholdings.

Still valid: https://firmenbuchdaten.at/api/v1/companies/{fnr}/persons

Plan: Business.

Parameters

Name	Type	Required	Description
`fnr`	string, path	yes	Register number with check letter, e.g. 508415w

Request

curl -H "Authorization: Bearer fbd_…" \
  "https://api.firmenbuchdaten.at/v1/companies/508415w/persons"

Response

{
  "fnr": "508415w",
  "functions": [
    {
      "key": "<key>",
      "name": "<Name>",
      "legalEntity": false,
      "code": "GF",
      "function": "<Funktion>",
      "since": "<JJJJ-MM-TT>",
      "representation": "<Vertretung>"
    }
  ],
  "endedFunctions": [],
  "source": "Österreichisches Firmenbuch, Republik Österreich, vertreten durch das BMJ, offene Daten unter CC BY 4.0"
}

Field	Type	Description
`fnr`	string	Register number
`functions[]`	array	key, name, legalEntity, code, function, since, representation
`endedFunctions[]`	array	key, name, legalEntity, code, function, since, notInExtractSince
`source`	string	Source line

Errors

Status	Code	Meaning
400	`invalid_fnr`	Not a valid register number.
403	`plan_without_persons`	Persons through the API come with Business only.
429	`person_rate`	Hourly or daily limit of person calls reached.

Change list API

Returns the companies with a new entry, a deletion, newly filed annual accounts or an edict in a period, or only for the companies you watch. This keeps your CRM current without querying every company.

GET `/v1/changes`

Changes in a period. Companies with a change in a period of at most 31 days, 100 per page. art: aenderung (newest entry in the period, new companies included), loeschung (deletion), abschluss (annual accounts filed), edikt. Per company the newest entry counts, not every single one; new entries on their own and changes of functions are planned.

Still valid: https://firmenbuchdaten.at/api/v1/changes

Plan: Business. One page is one call.

Parameters

Name	Type	Required	Description
`since`	string, query	yes	First day, YYYY-MM-DD
`until`	string, query	no	Last day, at most 31 days after since
`art`	string, query	no	aenderung (default), loeschung, abschluss or edikt
`rechtsform`	string, query	no	Legal form as in the register (not with edikt)
`sitz`	string, query	no	Seat as in the register (not with edikt)
`cursor`	string, query	no	nextCursor of the previous answer

Request

curl -H "Authorization: Bearer fbd_…" \
  "https://api.firmenbuchdaten.at/v1/changes?since=2026-11-01&until=2026-11-07&art=aenderung"

Response

{
  "since": "2026-11-01",
  "until": "2026-11-07",
  "art": "aenderung",
  "changes": [
    {
      "fnr": "508415w",
      "name": "RELACON GmbH",
      "kind": "aenderung",
      "date": "<JJJJ-MM-TT>",
      "sitz": "Klosterneuburg",
      "rechtsform": "Gesellschaft mit beschränkter Haftung",
      "description": "Eintragung im Firmenbuch"
    }
  ],
  "nextCursor": "<Cursor>",
  "source": "Österreichisches Firmenbuch, Republik Österreich, vertreten durch das BMJ, offene Daten unter CC BY 4.0"
}

Field	Type	Description
`since`	string	First day
`until`	string	Last day
`art`	string	Kind asked for
`changes[]`	array	fnr, name, kind, date (day of entry, filing or publication), sitz, rechtsform, description
`nextCursor`	string \| null	Value for cursor of the next page, null at the end
`source`	string	Source line

Errors

Status	Code	Meaning
400	`invalid_since`	since missing or not a date.
400	`range_too_long`	Period longer than 31 days.
400	`kind_not_available`	art=neueintragung or art=funktion: planned, not derivable today.
400	`unsupported_filter`	A parameter the list does not know (such as bundesland, bezirk, oenace).
403	`plan_without_changes`	The change list comes with Business; the watchlist with every plan.

GET `/v1/watchlist/changes`

Changes of watched companies. The same for the companies your account watches (Free 5, Pro 25, Business 250): newest entry, filed annual accounts and edicts since since, at most 93 days back.

Still valid: https://firmenbuchdaten.at/api/v1/watchlist/changes

Plan: All plans.

Parameters

Name	Type	Required	Description
`since`	string, query	yes	First day, YYYY-MM-DD

Request

curl -H "Authorization: Bearer fbd_…" \
  "https://api.firmenbuchdaten.at/v1/watchlist/changes?since=2026-11-01"

Response

{
  "since": "2026-11-01",
  "changes": [
    {
      "fnr": "508415w",
      "name": "RELACON GmbH",
      "kind": "abschluss",
      "date": "<JJJJ-MM-TT>",
      "sitz": "Klosterneuburg",
      "rechtsform": "Gesellschaft mit beschränkter Haftung",
      "description": "Jahresabschluss eingereicht"
    }
  ],
  "source": "Österreichisches Firmenbuch, Republik Österreich, vertreten durch das BMJ, offene Daten unter CC BY 4.0"
}

Field	Type	Description
`since`	string	First day
`changes[]`	array	as in /v1/changes, newest first
`source`	string	Source line

Errors

Status	Code	Meaning
400	`invalid_since`	since missing, not a date or in the future.
400	`range_too_long`	since lies too far back; the answer names the earliest day.

Customer check API

Gives a traffic light with payment term and the reasons for it, from the register, filings and the edict file. For the question: prepayment or invoice?

GET `/v1/kundencheck/{fnr}`

Customer check. The traffic light of the customer check with payment term and every signal (status, age, filing, size class, changes, edicts), each with German and English text. No amounts, no credit rating.

Still valid: https://firmenbuchdaten.at/api/v1/kundencheck/{fnr}

Plan: All plans. Business also: check against the EU sanctions list.

Parameters

Name	Type	Required	Description
`fnr`	string, path	yes	Register number with check letter, e.g. 508415w

Request

curl -H "Authorization: Bearer fbd_…" \
  "https://api.firmenbuchdaten.at/v1/kundencheck/508415w"

Response

{
  "fnr": "508415w",
  "name": "RELACON GmbH",
  "sitz": "Klosterneuburg",
  "rechtsform": "Gesellschaft mit beschränkter Haftung",
  "light": "<green | yellow | red>",
  "lightText": {
    "de": "<Text>",
    "en": "<text>"
  },
  "paymentTerm": "<vorkasse | 14 | 30>",
  "paymentTermText": {
    "de": "<Text>",
    "en": "<text>"
  },
  "registerRead": true,
  "signals": [
    {
      "key": "status",
      "level": "ok",
      "data": {
        "status": "active"
      },
      "de": "<Text>",
      "en": "<text>"
    }
  ],
  "sanctions": null,
  "fmaSanctions": [],
  "note": "<Hinweis>",
  "page": "https://firmenbuchdaten.at/kundencheck/508415w",
  "source": "Österreichisches Firmenbuch, Republik Österreich, vertreten durch das BMJ, offene Daten unter CC BY 4.0; Edikte: Republik Österreich, vertreten durch das BMJ (Ediktsdatei)"
}

Field	Type	Description
`fnr`	string	Register number
`name`	string	Company name
`sitz`	string	Seat according to the register
`rechtsform`	string	Legal form
`light`	string	green, yellow or red
`lightText`	object	Text for the light, de and en
`paymentTerm`	string	vorkasse (prepayment), 14 or 30 (days)
`paymentTermText`	object	Text for the payment term, de and en
`registerRead`	boolean	true when the register was read for this check
`signals[]`	array	Every signal with key, level, data and text de/en
`sanctions`	object \| null	Check against the EU sanctions list; null without Business or while no list is loaded
`fmaSanctions[]`	array	FMA sanctions against the company
`note`	string	Note: not a credit rating
`page`	string	Address of the customer check page
`source`	string	Source line

Errors

Status	Code	Meaning
400	`invalid_fnr`	Not a valid register number.
403	`sole_trader`	Sole traders are not checked; their name is a person's name.
404	`not_found`	No such register number.

VAT ID check (VIES)

Checks an EU VAT ID at VIES of the European Commission and names the name and address the member state shares, plus a cautious match with the register. Costs no call of the month.

GET `/v1/uid/{uid}`

Check a VAT ID. First the format and, for Austrian numbers, the check digit (without asking VIES), then VIES. state: gueltig (valid), ungueltig (not valid) or unerreichbar (VIES or the member state is not answering; never guessed). Answers are cached for 24 hours, unerreichbar never. match names a company of ours with the same name only as probable, because the register keeps no VAT IDs. Does not count against the monthly allowance; at most 100 checks per hour and account.

Still valid: https://firmenbuchdaten.at/api/v1/uid/{uid}

Plan: All plans, without a call from the allowance.

Parameters

Name	Type	Required	Description
`uid`	string, path	yes	VAT ID with country code, e.g. ATU12345678

Request

curl -H "Authorization: Bearer fbd_…" \
  "https://api.firmenbuchdaten.at/v1/uid/ATU74215057"

Response

{
  "uid": "ATU74215057",
  "state": "gueltig",
  "name": "RELACON GmbH",
  "address": "Preiseckergasse 5-7/3/12 AT-3420 Kritzendorf",
  "checkedAt": "2026-11-08T16:13:02.222Z",
  "match": {
    "fnr": "508415w",
    "name": "RELACON GmbH",
    "sitz": "Klosterneuburg",
    "confidence": "wahrscheinlich",
    "seatInAddress": false
  },
  "source": "VIES, European Commission (free, as of each query)"
}

Field	Type	Description
`uid`	string	The VAT ID in compact form
`state`	string	gueltig, ungueltig or unerreichbar
`name`	string \| null	Name according to VIES; null when the member state does not share it
`address`	string \| null	Address according to VIES
`checkedAt`	string	Time of the VIES answer (ISO 8601)
`match`	object \| null	fnr, name, sitz, confidence (always wahrscheinlich), seatInAddress
`source`	string	Source line

Errors

Status	Code	Meaning
400	`invalid_uid`	No EU country code or wrong length.
400	`invalid_check_digit`	Austrian VAT ID with a wrong check digit.
429	`uid_rate`	More than 100 VAT ID checks in an hour; Retry-After names the seconds.
429	`vies_busy`	The shared cap for requests to VIES is reached for this minute.

Errors any call can return

Status	Code	Meaning
401	`missing_or_invalid_key`	No or an invalid key in the Authorization header.
401	`invalid_key`	The key is revoked or unknown.
429	`monthly_credits_used`	This UTC month's calls are used up. The answer names limit and resetAt (Unix seconds, start of next month), plus the headers x-ratelimit-limit, x-ratelimit-remaining and x-ratelimit-reset.
503	`register_busy`	The register is paused and the company is not in our database yet. Try again later.

HTTP/1.1 429 Too Many Requests
x-ratelimit-limit: 50
x-ratelimit-remaining: 0
x-ratelimit-reset: 1796083200

{ "error": "monthly_credits_used", "limit": 50, "resetAt": 1796083200 }

MCP for AI assistants

So an AI assistant such as ChatGPT, Claude or Cursor can look things up in the register itself. Streamable HTTP at https://api.firmenbuchdaten.at/mcp (or https://firmenbuchdaten.at/mcp), the same key in the Authorization header. Tools: search_companies, get_company, get_financials. Every tool call costs one call.

{
  "mcpServers": {
    "firmenbuchdaten": {
      "type": "http",
      "url": "https://api.firmenbuchdaten.at/mcp",
      "headers": { "Authorization": "Bearer fbd_…" }
    }
  }
}

API overview API pricing

Source: Austrian company register (Firmenbuch), Republic of Austria, represented by the BMJ, open data under CC BY 4.0.

Documentation of the register API

Access and authentication

Company API

GET /v1/companies

Parameters

Request

Response

Errors

GET /v1/companies/{fnr}

Parameters

Request

Response

Errors

GET /v1/companies/{fnr}/gewerbe

Parameters

Request

Response

Errors

Annual accounts API

GET /v1/companies/{fnr}/financials

Parameters

Request

Response

Errors

GET /v1/companies/{fnr}/documents/{stichtag}

Parameters

Request

Response

Errors

Person API

GET /v1/persons

Parameters

Request

Response

Errors

GET /v1/persons/{key}

Parameters

Request

Response

Errors

GET /v1/companies/{fnr}/persons

Parameters

Request

Response

Errors

Change list API

GET /v1/changes

Parameters

Request

Response

Errors

GET /v1/watchlist/changes

Parameters

Request

Response

Errors

Customer check API

GET /v1/kundencheck/{fnr}

Parameters

Request

Response

Errors

VAT ID check (VIES)

GET /v1/uid/{uid}

Parameters

Request

Response

Errors

Errors any call can return

MCP for AI assistants

GET `/v1/companies`

GET `/v1/companies/{fnr}`

GET `/v1/companies/{fnr}/gewerbe`

GET `/v1/companies/{fnr}/financials`

GET `/v1/companies/{fnr}/documents/{stichtag}`

GET `/v1/persons`

GET `/v1/persons/{key}`

GET `/v1/companies/{fnr}/persons`

GET `/v1/changes`

GET `/v1/watchlist/changes`

GET `/v1/kundencheck/{fnr}`

GET `/v1/uid/{uid}`