Companies House, OpenCorporates, OpenRegistry or us: which to use

There are four realistic ways to get UK company data into software, and a fair amount of marketing pretending there is only one. This page is our attempt at the comparison we wanted when we started, including the parts where we lose.

Everything here was checked on 24 September 2026. We sell one of these tools, which is a conflict of interest you should assume is present in every line.

The four options

Companies House's own API is free, official and the source everyone else derives from. It has no rate-limit cost, no vendor, and no risk of a middleman being out of date, because there is no middleman. What you get is the raw register: profiles, officers, PSCs, filing lists, and accounts as filed. Accounts arrive as iXBRL documents or, for a large minority of companies, as scanned images. Turning those into numbers is your problem. So is following an ownership chain through five holding companies, which is five or more separate calls you orchestrate yourself.

OpenRegistry covers many national registries through a single endpoint and an MCP server, with a free anonymous tier. Its explicit design position is that it returns upstream data verbatim and does not normalise or parse it - their documentation says a filing's content is "the literal iXBRL bytes Companies House sends". If you want breadth across jurisdictions, or you specifically want unmodified bytes, this is a reasonable answer and better than us at both.

OpenCorporates is the long-established open-data aggregator, with far wider jurisdictional coverage than we will ever have. It is a database built from registry snapshots, so how current any given record is depends on its refresh cycle rather than on the register itself. For cross-border research at scale, it is the incumbent for good reasons.

Registrum does one country properly. UK only, API-first, with the register's raw data plus three things we do to it: accounts parsed into comparable financial figures, ownership chains followed to the people at the end, and identity-verification status read per person.

Side by side

	Companies House	OpenRegistry	OpenCorporates	Registrum
Jurisdictions	UK	many	many	UK only
Authority	the source	passthrough	aggregated snapshots	derived, live
Accounts	as filed (iXBRL or image)	raw bytes, by design	varies	parsed into figures
Ownership chain	PSCs per company, you traverse	per company	per company	traversed to individuals
Identity verification	per person on the record	raw fields	not a focus	read per person, per company
Access	free API key	free tier, MCP	free and paid tiers	free tier, paid plans, MCP
Cost	free	free tier of 30 requests/min; no pricing page published	published pricing	our pricing

When we are the wrong choice

Worth saying plainly, because a comparison table where one column wins every row is an advertisement:

• You need data outside the UK. We have nothing. Use OpenCorporates or OpenRegistry.
• You need the unmodified filing as evidence. For audit, litigation or anything where a regulator may ask what the company actually filed, you want the original document, not our reading of it. Take it from Companies House directly.
• You need credit scores, ratings or director disqualification history. We hold none of these. That is what Creditsafe, Endole and the Insolvency Service's own register are for.
• You are looking up one company, once. Use the free Companies House website. Paying for an API to answer a question you can answer in a browser is silly.

What we would argue we are better at

Parsed accounts. Handing an LLM a raw iXBRL document and asking for turnover is the single most common way people get a wrong number, because the parsing is non-deterministic and a confidently wrong revenue figure is worse than no figure. Our parser is versioned, tested against real filings, and returns an explicit "not available" rather than a guess when a filing genuinely does not contain the number. That is a narrower promise than it sounds, and it is the right one.

Ownership to the end of the chain. Most tools show a company's immediate PSCs. When those PSCs are themselves companies, the question a human actually asked - who owns this - is still unanswered. We keep going until we reach individuals.

Identity verification per person. Verification status is published per director and per PSC, and it is not a single company-level yes or no. Getting that distinction wrong tells someone to chase a person who has already complied.

Checking any of this yourself

• Every claim about Companies House's API is testable against their free developer service at developer.company-information.service.gov.uk.
• OpenCorporates publishes its prices at opencorporates.com/pricing. OpenRegistry publishes a free tier of 30 requests per minute but, as at 24 September 2026, no pricing page at all - we looked through their sitemap. We have deliberately not restated anyone's prices here, because copied prices go stale and theirs are one click away.
• Our side is testable without an account: the keyless MCP endpoint at https://registrum.co.uk/api/mcp and any company page, for example https://registrum.co.uk/company/00445790.

If you find something in the table above that is wrong or out of date, tell us and we will correct it and date the correction.