REGON (Poland)

GET/v0/pl/regon

Validates Polish statistical identification numbers (REGON). Supports both the 9-digit format used by legal entities and the 14-digit format used by local units. Verification is based on the official checksum algorithm. Optionally performs a live lookup against the official Polish government GUS BIR (REGON) registry to retrieve entity details such as name, NIP, and address.

Guides: Node.js · Python

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Query Parameters

Parameter	Type	Required	Description
value	string	Yes	The 9-digit or 14-digit REGON number to validate
lookup	boolean	No	When `true`, performs a live lookup against the official Polish GUS BIR (REGON) government API and returns entity details.

Example Request

curl -H "Authorization: Bearer YOUR_API_KEY" \
  "https://api.isvalid.dev/v0/pl/regon?value=590096454&lookup=true"

Response Fields

Field	Type	Description
valid	boolean	Whether the REGON number is valid (checksum correct)
type	string	Format variant: `entity` (9-digit) or `local-unit` (14-digit). Only present when valid is `true`.
regon	object	Live lookup result. Present only when `lookup=true`. See The `regon` object below.

The `regon` object

When the lookup failed (checked: false):

Field	Type	Description
checked	boolean	`false`
reason	string	`unavailable` — the GUS BIR API could not be reached

When the lookup succeeded (checked: true):

Field	Type	Description
checked	boolean	`true`
found	boolean	Whether the entity was found in the REGON registry
name	string \| null	Registered name of the entity
nip	string \| null	Tax identification number (NIP)
voivodeship	string \| null	Voivodeship (province)
district	string \| null	District (powiat)
community	string \| null	Community (gmina)
city	string \| null	City or town
postalCode	string \| null	Postal code
street	string \| null	Street name
houseNumber	string \| null	Building/house number
flatNumber	string \| null	Flat/apartment number
activityEndDate	string \| null	Date when the entity ceased activity (null if still active)

Example Response

{
  "valid": true,
  "type": "entity",
  "regon": {
    "checked": true,
    "found": true,
    "name": "T-MOBILE POLSKA SPÓŁKA AKCYJNA",
    "nip": "5260250995",
    "voivodeship": "MAZOWIECKIE",
    "district": "m. st. Warszawa",
    "community": "Ochota",
    "city": "Warszawa",
    "postalCode": "02-326",
    "street": "ul. Aleje Jerozolimskie",
    "houseNumber": "160",
    "flatNumber": null,
    "activityEndDate": null
  }
}