SW1Y 5AA

30 companies are registered at SW1Y 5AA on the Companies House register. A postcode covers roughly fifteen addresses, so a high count usually means one building — a formation agent, an accountant or a serviced office — rather than a busy street.

A registered office is where official post is served, not where the business happens. Formation agents and accountants offer their own address for that purpose, so a single building can hold thousands of registrations. It says nothing about any of them on its own — but it does mean the address tells you nothing about the business either.

Not necessarily. The register records the registered office, which is a legal address for service. Many companies trade somewhere else entirely, and nothing requires the two to match.

The ONS Postcode Directory, which places every UK postcode. The companies come from the Companies House register. Both are published as open data and refreshed on a schedule — a company incorporated in the last day or so may not be here yet.