castomAPI
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POST /v1/verify/company 2 tokens API key Verify

Verify B2B company registration numbers

Verify B2B company registration numbers, check trade register structure (UK Companies House, France SIREN/SIRET, Poland KRS, Germany Handelsregister, US DUNS/SOS), validate Luhn checksums, and infer legal entity structure

POST

Request

  • x-api-key: <your-api-key>
  • Content-Type: application/json

Response

{
  "companyDetails": {
    "countryCode": "PL",
    "entityType": "standard",
    "expectedFormatExample": "<expected format example>",
    "normalizedRegistrationNumber": "PL61109010140000071219812874",
    "officialRegistryUrl": "https://example.com/page",
    "rawInput": "PL61109010140000071219812874",
    "registryAuthority": "<registry authority>"
  },
  "isValid": true,
  "status": "success",
  "tokensDeducted": 2,
  "validationResult": {
    "isChecksumValid": true,
    "isFormatValid": true,
    "jurisdictionDetected": "<jurisdiction detected>",
    "reason": "checksum ok"
  }
}
The response below is a mock built from the endpoint's own schema — no request leaves this page. Edit the body, press Send, read the shape you will get back. Run it for real in the dashboard →

What it does

Verify B2B company registration numbers, check trade register structure (UK Companies House, France SIREN/SIRET, Poland KRS, Germany Handelsregister, US DUNS/SOS), validate Luhn checksums, and infer legal entity structure

Request

Body

FieldTypeRequiredDescription
companyNamestringnoOptional company name for entity type classification and verification context.
countryCodestringnoOptional 2-letter ISO country code (e.g. "GB", "FR", "PL", "DE", "US"). Auto-detected if omitted.
registrationNumberstringyesTrade registry identification number (e.g., "00059707", "732829320", "0000123456", "HRB 12345", or "1234567")

Example request

{
  "companyName": "Castomo P.S.A.",
  "countryCode": "PL",
  "registrationNumber": "<registration number>"
}

Response

FieldTypeDescription
companyDetailsobject
  ↳ countryCodestring
  ↳ entityTypestring
  ↳ expectedFormatExamplestring
  ↳ normalizedRegistrationNumberstring
  ↳ officialRegistryUrlstring
  ↳ rawInputstring
  ↳ registryAuthoritystring
isValidboolean
statusstring
tokensDeductedinteger
validationResultobject
  ↳ isChecksumValidboolean
  ↳ isFormatValidboolean
  ↳ jurisdictionDetectedstring
  ↳ reasonstring

Example response

{
  "companyDetails": {
    "countryCode": "PL",
    "entityType": "standard",
    "expectedFormatExample": "<expected format example>",
    "normalizedRegistrationNumber": "PL61109010140000071219812874",
    "officialRegistryUrl": "https://example.com/page",
    "rawInput": "PL61109010140000071219812874",
    "registryAuthority": "<registry authority>"
  },
  "isValid": true,
  "status": "success",
  "tokensDeducted": 2,
  "validationResult": {
    "isChecksumValid": true,
    "isFormatValid": true,
    "jurisdictionDetected": "<jurisdiction detected>",
    "reason": "checksum ok"
  }
}

Errors

Every error answers with the same envelope: an HTTP status, a machine code and a sentence.

400The body or a parameter failed validation. The details array names the field.
401No key, a revoked key or a wrong header. Send x-api-key.
402The wallet cannot cover this call. Top up or wait for the monthly grant.
404The resource does not exist, or it is not yours. Both answer identically and cost nothing.
429Over the per-minute quota of your tier. Back off and retry.
5xxUpstream refused or timed out. The call is not billed.

Code

curl -X POST 'https://app.castomapi.com/v1/verify/company' \
  -H 'x-api-key: <your-api-key>' \
  -H 'Content-Type: application/json' \
  -d '{"companyName": "Castomo P.S.A.", "countryCode": "PL", "registrationNumber": "<registration number>"}'
const res = await fetch('https://app.castomapi.com/v1/verify/company', {
  method: 'POST',
  headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
  body: JSON.stringify({"companyName": "Castomo P.S.A.", "countryCode": "PL", "registrationNumber": "<registration number>"})
});
const data = await res.json();
console.log(data);
import { request } from 'node:https';

// Node 18+ has fetch built in
const res = await fetch('https://app.castomapi.com/v1/verify/company', {
  method: 'POST',
  headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
  body: JSON.stringify({"companyName": "Castomo P.S.A.", "countryCode": "PL", "registrationNumber": "<registration number>"})
});
const data = await res.json();
console.log(data);
import requests

res = requests.post(
    'https://app.castomapi.com/v1/verify/company',
    headers={'x-api-key': '<your-api-key>'},
    json={"companyName": "Castomo P.S.A.", "countryCode": "PL", "registrationNumber": "<registration number>"},
    timeout=30,
)
print(res.json())
<?php
$ch = curl_init('https://app.castomapi.com/v1/verify/company');
curl_setopt_array($ch, [
    CURLOPT_CUSTOMREQUEST => 'POST',
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ['x-api-key: <your-api-key>', 'Content-Type: application/json'],
    CURLOPT_POSTFIELDS => json_encode(['companyName' => 'Castomo P.S.A.', 'countryCode' => 'PL', 'registrationNumber' => '<registration number>']),
]);
$data = json_decode(curl_exec($ch), true);
print_r($data);

Cost and limits

This operation costs 2 tokens. A call that fails is never billed. Every account gets 1000 free tokens a month; paid balances never expire.

Rate limits per minute

No key10
Free60
Pro300
Enterprise1200

Docs → Pricing

Questions

What does Verify B2B company registration numbers cost?

2 tokens per successful call, debited from your wallet after the response. Failed calls are free. Every account receives 1000 free tokens a month.

How do I authenticate?

Send your key in the x-api-key header. One key covers every metered endpoint; there is nothing to enable per endpoint.

Can I send an Authorization: Bearer token instead?

Not for a metered endpoint — those take the x-api-key header and nothing else. Bearer tokens belong to the account side: the dashboard and account APIs accept a JWT session, and castomapi-auth issues those through a standard OAuth2 handshake, with authorization code, client credentials and refresh grants. The auth service page covers it.

What are the limits?

10 requests a minute per IP with no key at all, 60 a minute on the free tier, 300 on Pro, 1200 on Enterprise. Above the no-key tier the quota is per account, across every endpoint.

OpenAPI: https://app.castomapi.com/docs/json