ch-api 0.0.0.dev0

Pythonic Company House API

Companies House API Python Client

A comprehensive, asynchronous Python client for the Companies House API, providing real-time access to UK company information including profiles, officers, charges, filing history, and persons with significant control.

Features

• Full async/await support using httpx
• Automatic pagination handling for large result sets
• Type-safe Pydantic models for all API responses
• Support for all Companies House API endpoints
• Optional rate limiting support
• Comprehensive error handling
• Production-ready and well-tested

Supported Data

The client provides access to:

• Company profiles and status information
• Registered office addresses
• Director and officer information
• Officer appointment history
• Persons with Significant Control (PSC)
• Charges over company assets
• Filing history and documents
• Financial accounts information
• Exemptions from filing
• Insolvency proceedings
• Disqualified officers
• UK branch establishments

Installation

Install from PyPI:

pip install ch-api

Or install from source:

git clone https://github.com/yourusername/ch-api.git
cd ch-api
pip install -e .

Requirements

• Python 3.11 or later
• httpx >= 0.28.1
• pydantic >= 2.12.5

Quick Start

1. Get an API Key

Register at the Companies House Developer Portal to obtain your API key: https://developer.company-information.service.gov.uk/

2. Create a Client

from ch_api import Client, api_settings

# Create authentication settings
auth = api_settings.AuthSettings(api_key="your-api-key")

# Create the client (uses production API by default)
client = Client(credentials=auth)

3. Fetch Company Information

# Get company profile
company = await client.get_company_profile("09370755")
print(f"Company: {company.company_name}")
print(f"Status: {company.company_status}")
print(f"Type: {company.company_type}")

# Get registered office address
address = await client.registered_office_address("09370755")
print(f"Address: {address.address_line_1}")
print(f"Postcode: {address.postal_code}")

4. Search for Companies

# Simple search
results = await client.search_companies("Apple")
print(f"Total results: {len(results)}")

# Iterate through results (pages fetched automatically)
async for company in results:
    print(f"{company.title} ({company.company_number})")

# Access specific results by index
if len(results) > 0:
    first = results[0]
    print(f"First result: {first.title}")

5. Get Company Officers

# Get list of officers
officers = await client.get_officer_list("09370755")

# Iterate through officers
async for officer in officers:
    print(f"{officer.name}")
    print(f"  Appointed: {officer.appointed_on}")
    print(f"  Role: {officer.officer_role}")

# Filter by officer type
directors = await client.get_officer_list(
    "09370755",
    only_type="directors"
)

6. Get Filing History

# Get all filing history
filings = await client.get_company_filing_history("09370755")

# Iterate through filings
async for filing in filings:
    print(f"{filing.type} - {filing.date}")

# Filter by category
accounts = await client.get_company_filing_history(
    "09370755",
    categories=("accounts", "annual-return")
)

7. Get Charges

# Get all charges
charges = await client.get_company_charges("09370755")

for charge in charges.items or []:
    print(f"Charge {charge.charge_number}")
    print(f"  Type: {charge.charge_code}")
    print(f"  Date: {charge.created_on}")

# Get specific charge details
details = await client.get_company_charge_details("09370755", "charge-id")

8. Get Persons with Significant Control

# Get PSC list
psc_list = await client.get_company_psc_list("09370755")

# Iterate through PSCs
async for psc in psc_list.items:
    print(f"{psc.name}")
    print(f"  Nature of control: {psc.nature_of_control}")

# Get specific PSC details
psc = await client.get_company_individual_psc("09370755", "psc-id")

Advanced Usage

Using Different Environments

Switch between production and sandbox environments:

from ch_api import Client, api_settings

auth = api_settings.AuthSettings(api_key="your-api-key")

# Production (default)
client = Client(credentials=auth, settings=api_settings.LIVE_API_SETTINGS)

# Sandbox for testing
client = Client(credentials=auth, settings=api_settings.TEST_API_SETTINGS)

Rate Limiting

Control API request rate with asyncio-throttle or similar:

from ch_api import Client, api_settings
import asyncio_throttle

auth = api_settings.AuthSettings(api_key="your-api-key")

# Create rate limiter (max 2 requests per second)
limiter = asyncio_throttle.AsyncThrottle(max_rate=2, time_period=1.0)

# Create client with rate limiter
client = Client(
    credentials=auth,
    api_limiter=lambda: limiter
)

Advanced Company Search

Perform advanced searches with multiple filters:

import datetime

results = await client.advanced_company_search(
    company_name_includes="Technology",
    company_name_excludes="Holdings",
    company_status="active",
    company_type="private-unlimited",
    location="England",
    sic_codes=["62012"],
    incorporated_from=datetime.date(2020, 1, 1),
    max_results=100
)

async for company in results:
    print(f"{company.company_name}")

Alphabetical Search

Browse companies alphabetically:

results = await client.alphabetical_companies_search(
    query="BBC",
    page_size=20
)

async for company in results:
    print(f"{company.title}")

Dissolved Company Search

Search for dissolved or historical companies:

results = await client.search_dissolved_companies(
    query="Enron",
    search_type="best-match"
)

async for company in results:
    print(f"{company.title}")
    print(f"  Dissolved: {company.date_of_dissolution}")

Prefetch All Pages

For better performance with bulk operations, prefetch all pages:

results = await client.search_companies("Technology")

# Fetch all pages at once
await results.fetch_all_pages()

# Access all items without further API calls
for item in results.local_items():
    process(item)

API Reference

Client Methods

Company Information

• get_company_profile(company_number) - Get company profile
• registered_office_address(company_number) - Get registered office address
• get_company_registers(company_number) - Get company registers information

Officers

• get_officer_list(company_number, only_type=None, order_by=None) - Get officers list
• get_officer_appointment(company_number, appointment_id) - Get officer appointment details
• get_officer_appointments(officer_id) - Get officer's appointments across companies
• get_corporate_officer_disqualification(officer_id) - Get corporate disqualification
• get_natural_officer_disqualification(officer_id) - Get natural person disqualification

Persons with Significant Control

• get_company_psc_list(company_number) - Get PSC list
• get_company_psc_statements(company_number) - Get PSC statements
• get_company_individual_psc(company_number, psc_id) - Get individual PSC
• get_company_corporate_psc(company_number, psc_id) - Get corporate PSC
• get_company_legal_person_psc(company_number, psc_id) - Get legal person PSC
• Additional PSC-related methods for beneficial owners and super-secure PSCs

Financial & Legal

• get_company_charges(company_number) - Get all charges
• get_company_charge_details(company_number, charge_id) - Get charge details
• get_company_filing_history(company_number, categories=None) - Get filing history
• get_filing_history_item(company_number, filing_id) - Get filing details
• get_company_exemptions(company_number) - Get exemptions
• get_company_insolvency(company_number) - Get insolvency information

Search

• search(query) - General search (companies and officers)
• search_companies(query) - Search companies
• search_officers(query) - Search officers
• search_disqualified_officers(query) - Search disqualified officers
• advanced_company_search(...) - Advanced search with filters
• alphabetical_companies_search(query) - Alphabetical search
• search_dissolved_companies(query) - Search dissolved companies

Other

• get_company_uk_establishments(company_number) - Get UK branch establishments
• create_test_company(company) - Create test company (sandbox only)

Response Types

All API endpoints return Pydantic models providing:

• Type validation
• IDE autocomplete support
• Easy serialization/deserialization
• Helpful error messages

For detailed information about response types, see the types documentation.

Error Handling

The client defines custom exceptions:

from ch_api import exc

try:
    profile = await client.get_company_profile("invalid-number")
except exc.UnexpectedApiResponseError as e:
    print(f"API response was unexpected: {e}")
except exc.CompaniesHouseApiError as e:
    print(f"API error occurred: {e}")

Configuration

Authentication Settings

from ch_api.api_settings import AuthSettings

auth = AuthSettings(api_key="your-api-key")

API Settings

from ch_api.api_settings import LIVE_API_SETTINGS, TEST_API_SETTINGS

# Production (default)
settings = LIVE_API_SETTINGS

# Sandbox
settings = TEST_API_SETTINGS

Async/Await Pattern

All client methods are asynchronous and must be called with await:

import asyncio

async def main():
    client = Client(credentials=auth)
    
    # Use await for async methods
    profile = await client.get_company_profile("09370755")
    print(profile.company_name)
    
    # Use async for for paginated results
    results = await client.search_companies("Apple")
    async for company in results:
        print(company.title)

# Run the async function
asyncio.run(main())

Pagination

List and search endpoints return MultipageList objects that provide:

• Lazy loading: Pages fetched only when accessed
• Length checking: len(results) returns total count
• Indexing: results[0] fetches items on demand
• Async iteration: async for item in results
• All-at-once: await results.fetch_all_pages()

results = await client.search_companies("Apple")

# Check total without loading all pages
total = len(results)

# Iterate (loads pages as needed)
async for company in results:
    print(company.title)

# Access by index
first = results[0]

# Prefetch all
await results.fetch_all_pages()
for company in results.local_items():
    print(company.title)

API Rate Limiting

The Companies House API enforces rate limits. Consider using a rate limiter:

pip install asyncio-throttle

import asyncio_throttle

limiter = asyncio_throttle.AsyncThrottle(max_rate=5, time_period=1.0)
client = Client(credentials=auth, api_limiter=lambda: limiter)

Performance Tips

1. Use prefetching for bulk operations:

   await results.fetch_all_pages()
   

2. Filter results server-side when possible:

   # Better: filter via parameters
   await client.get_officer_list("09370755", only_type="directors")
   

3. Use appropriate page sizes for your use case

4. Reuse client instances to maintain connection pooling

5. Consider using a rate limiter to avoid hitting API limits

Testing

For development and testing, use the sandbox API:

from ch_api import api_settings

auth = api_settings.AuthSettings(api_key="your-sandbox-key")
client = Client(credentials=auth, settings=api_settings.TEST_API_SETTINGS)

# Test data can be created in the sandbox
# See API documentation for details

Project Structure

src/ch_api/
├── __init__.py              # Package entry point
├── api.py                   # Main Client class
├── api_settings.py          # Configuration classes
├── exc.py                   # Exception types
└── types/                   # Type definitions
    ├── base.py              # Base Pydantic model
    ├── field_types.py       # Custom field types
    ├── shared.py            # Shared types
    ├── settings.py          # Global configuration
    ├── pagination/          # Pagination types
    ├── public_data/         # API response models
    │   ├── company_profile.py
    │   ├── search.py
    │   ├── company_officers.py
    │   ├── charges.py
    │   ├── filing_history.py
    │   ├── psc.py
    │   └── ...
    └── compound_api_types/  # Complex wrappers

Documentation

• Complete API reference with docstrings: src/ch_api/
• Type documentation: src/ch_api/types/
• Companies House API: https://developer-specs.company-information.service.gov.uk/
• API Swagger specs: https://developer-specs.company-information.service.gov.uk/api.ch.gov.uk-specifications/swagger-2.0/spec/swagger.json

Common Patterns

Fetch and Process All Companies in a List

results = await client.search_companies("Technology")
await results.fetch_all_pages()

for company in results.local_items():
    profile = await client.get_company_profile(company.company_number)
    print(f"{profile.company_name}: {profile.company_status}")

Monitor Company Changes

async def check_company_status(company_number, interval_hours=24):
    import asyncio
    
    client = Client(credentials=auth)
    
    while True:
        profile = await client.get_company_profile(company_number)
        print(f"Status: {profile.company_status}")
        
        await asyncio.sleep(interval_hours * 3600)

Export Company Data

import json

company = await client.get_company_profile("09370755")

# Pydantic models serialize to dict/JSON easily
company_dict = company.model_dump()
company_json = company.model_dump_json()

print(json.dumps(company_dict, indent=2))

Troubleshooting

Authentication Error

Ensure your API key is correct:

auth = api_settings.AuthSettings(api_key="your-correct-key")

Rate Limit Error

Implement rate limiting:

from ch_api import Client, api_settings
import asyncio_throttle

limiter = asyncio_throttle.AsyncThrottle(max_rate=2, time_period=1.0)
client = Client(credentials=auth, api_limiter=lambda: limiter)

No Results Found

Check company number format (8 alphanumeric characters):

profile = await client.get_company_profile("09370755")  # Correct format

Timeout Errors

Use a custom httpx.AsyncClient with timeout settings:

import httpx
from ch_api import Client, api_settings

auth = api_settings.AuthSettings(api_key="your-key")
http_client = httpx.AsyncClient(timeout=30.0)
client = Client(credentials=http_client)

Contributing

Contributions are welcome. Please:

1. Fork the repository
2. Create a feature branch
3. Add tests for new functionality
4. Ensure code follows project style
5. Submit a pull request

License

MIT License - see LICENSE file for details

Support

For issues and questions:

• GitHub Issues: https://github.com/yourusername/ch-api/issues
• Companies House API Support: https://developer-specs.company-information.service.gov.uk/
• Companies House Developer Forum: https://forum.aws.chdev.org/

Changelog

See CHANGELOG.md for version history and updates.

Related Projects

• Companies House API Enumerations
• Official API Documentation: https://developer-specs.company-information.service.gov.uk/
• Companies House: https://www.companieshouse.gov.uk/