Companies House API vs Manual Research: Which Is Better for Lead Generation?

If you're trying to find new business leads using public company data, you have a fundamental choice to make: build it yourself using the Companies House API, do it manually through the Companies House website, or use a service that does the heavy lifting for you.

Each approach has trade-offs in terms of cost, time, data quality, and scalability. In this article, we'll walk through the technical realities of each option so you can make an informed decision.

Option 1: manual research via the Companies House website

The simplest approach. Visit find-and-update.company-information.service.gov.uk, search for a company by name or number, and view its details.

What you can do

• Search for individual companies by name or number
• View company profiles, officer details, and filing history
• Download individual filed documents (accounts, confirmation statements)
• Search for officers by name

What you can't do

• Search for "all companies incorporated today"
• Filter by SIC code, date range, or region
• Export data in bulk
• Set up automated alerts for new incorporations

Verdict: Fine for looking up a specific company. Completely impractical for lead generation. You'd need to search one company at a time, with no way to discover newly incorporated companies systematically.

Option 2: building with the Companies House API

Companies House provides a free REST API that allows programmatic access to its data. If you have development skills (or access to a developer), you can build a custom solution for extracting new company data.

Getting started

To use the API, you need to:

1. Register for an API key at the Companies House developer portal
2. Choose your approach: the REST API for ad-hoc queries, the Streaming API for real-time events, or the bulk data products for full database downloads
3. Build your application to query the data, process it, and output it in a usable format

The REST API

The standard REST API provides endpoints for searching companies, retrieving company profiles, listing officers, viewing filing history, and accessing charges and PSC data.

The key limitation for lead generation is that there's no "get all new companies" endpoint. You can search for companies by name or number, but you can't request a list of all companies incorporated on a given date. This makes the REST API alone insufficient for systematic new company lead generation.

The Streaming API

This is more useful for lead generation. The Streaming API provides real-time event streams for company filings, company profile changes (including new incorporations), officer appointments, and PSC notifications.

By subscribing to the company profile stream, you can capture new incorporations as they're registered. However, this requires:

• A persistent connection — your application needs to maintain a long-lived HTTP connection to the stream
• Server infrastructure — you need a server running 24/7 to receive and store the data
• Data processing logic — the stream includes all profile changes, not just new incorporations. You need to filter for the events you want.
• Error handling and recovery — if your connection drops, you need to handle reconnection and avoid missing events

Rate limits

The Companies House API enforces rate limits to prevent abuse:

The 600 requests per five minutes limit on the REST API means that if you want to enrich each new company with additional data (officer details, for instance), you're limited to processing approximately 120 companies per minute. On a busy day with 2,500+ new incorporations, enriching every company takes around 20 minutes — assuming no errors or retries.

The real cost of DIY

While the API itself is free, building and maintaining a production-quality lead generation system involves significant hidden costs:

At a conservative developer rate of £50/hour, the initial build alone costs £2,000-4,000, with ongoing maintenance adding £100-250/month in developer time. That's before accounting for the opportunity cost of your time if you're building it yourself.

Data quality challenges

Even with a working system, you'll encounter data quality issues that require handling:

• Incomplete records: Some new incorporations appear with minimal data initially, requiring follow-up queries to get full details
• SIC code inconsistencies: Companies can declare SIC codes that don't exist in the official classification or use generic catch-all codes
• Address formatting: Registered addresses come in varying formats and require normalisation for any mail-merge or mapping use
• Duplicate events: The streaming API can occasionally deliver duplicate events, requiring deduplication logic
• Weekend and bank holiday gaps: Companies House doesn't process incorporations over weekends, leading to batch appearances on Mondays

Option 3: using a data service

The third option is to use a service that has already solved these technical challenges and delivers ready-to-use new company data. NewCo Data is one such service, specifically focused on new company incorporation data for lead generation.

How it works

Services like NewCo Data pull data from Companies House daily (using the API, streaming feeds, and bulk products), process and clean the data, enrich it with full officer details and formatted addresses, classify it by sector using SIC codes, and deliver filtered reports to subscribers via email.

You specify the sectors you're interested in and receive a daily email containing only the relevant new incorporations, with all the data you need for outreach: company name, director name, registered address, SIC code, and Companies House link.

Cost comparison

When should you build vs buy?

Build your own if:

• You have specific data requirements that go beyond what any service offers
• You need to integrate company data into a larger custom platform
• You have in-house development resources with spare capacity
• You're building a product that relies on company data (i.e., you're becoming a data provider yourself)

Use a service if:

• Your primary goal is lead generation, not building technology
• You want to start receiving leads today, not in 6-8 weeks
• You don't have development resources (or would rather spend them on your core product)
• You want reliable, daily data without the maintenance burden
• The cost of a service (from £29/month) is a fraction of what you'd spend building and maintaining your own solution

For most B2B service providers — accountants, insurance brokers, web agencies, telecom providers — building a custom API integration is significant over-engineering for what is ultimately a simple need: "Show me the new companies in my sector, every day."

Key takeaways

Manual research via the Companies House website is impractical for lead generation — there's no way to discover new companies systematically. The Companies House API is powerful but complex, requiring significant development time, server infrastructure, and ongoing maintenance. Building a DIY solution costs £3,000-5,000+ in development time, plus ongoing hosting and maintenance. Rate limits and data quality issues add further complexity to API-based approaches. For most businesses, using a data service like NewCo Data (from £29/month) is significantly cheaper and faster than building a custom solution — and lets you focus on outreach rather than infrastructure.