Companies House API — Key Endpoints
Companies House API is completely free — no usage charges, no rate limit tiers. Rate limiting applies (600 requests per 5 minutes per API key). Register at developer.company-information.service.gov.uk for an API key.
| Endpoint | Description | Key Use Cases |
|---|---|---|
| /search/companies?q={query} | Search for companies by name or number | KYC company lookup, company verification, autocomplete |
| /company/{company_number} | Full company profile | Registration status, SIC codes, registered address, accounts due |
| /company/{company_number}/officers | List of current and former officers | Director verification, officer search, AML beneficial ownership |
| /company/{company_number}/persons-with-significant-control | PSC register (beneficial ownership) | AML/KYC beneficial ownership, 25%+ shareholders |
| /company/{company_number}/filing-history | All filed documents (accounts, confirmation statements) | Credit assessment, compliance checks, document access |
| /company/{company_number}/charges | Mortgages and charges on the company | Secured lending, conveyancing, credit risk |
| /search/officers?q={query} | Search for officers by name | Individual KYC, director search, disqualification check |
| /officers/{officer_id}/appointments | All company appointments for an officer | Director network analysis, group structure research |
AML/KYC Use Cases
Company identity verification: registered name, registration number, registered address, and incorporation date — all verified against Companies House.
Beneficial ownership: PSC API returns individuals with 25%+ ownership or control — direct evidence of beneficial ownership for AML CDD.
Director identity: officer search cross-referenced with personal identity verification (Onfido or equivalent).
Disqualified directors: Companies House maintains a disqualified directors register — check via officer search.
Active company status: confirmation that company is not dissolved, in administration, or struck off before onboarding.
Companies House API is a cornerstone of UK AML and KYC processes under MLRs 2017:
UK GDPR and Companies House Data
Officer personal data: home addresses are sometimes included in officer filings. UK GDPR applies to processing officer personal data. Companies House provides address suppression for officers at risk.
PSC data: individuals with significant control have their personal data (name, address, nationality) published. Lawful basis for processing in your system: legitimate interest (AML/KYC compliance obligation under MLRs 2017).
Storing Companies House data: if you store company/officer data in your own database, it becomes your personal data processing — UK GDPR obligations apply including retention policies.
Companies House data is largely public information — company registration details, filing history, and charges are public record. However:
Rate Limiting and Best Practices
| Consideration | Detail | Best Practice |
|---|---|---|
| Rate limit | 600 requests per 5-minute window per API key | Cache responses (company data changes slowly). Use multiple API keys for high-volume applications. |
| Response caching | Company data rarely changes | Cache company profiles for 24 hours. Cache PSC/officers for 1 hour. Always re-fetch before KYC sign-off. |
| Pagination | Most list endpoints paginate | Handle start_index parameter. Default page size: 35 items. |
| Error handling | 404 = company not found; 429 = rate limited | Implement exponential backoff for 429. Log 404s — may indicate fraudulent company number. |
| Streaming companies | Full company register download available | Use bulk download for large-scale analysis; not the API. |