Eight Characters of Provenance: What the Company Number Prefix Actually Encodes About a UK Entity

Every entity on the Companies House register carries an eight-character identifier. To most directors it is a string they paste into search boxes; to compliance teams and due-diligence analysts it is the most stable signal Companies House ever issues. Names change, registered offices move, directors come and go, but the number allocated under section 1066 of the Companies Act 2006 follows a company from incorporation to dissolution and — if it ever happens — restoration.

This piece reads the number itself: the prefix system that distinguishes jurisdictions and entity types, the sequence that runs from a Victorian start at 00000001 to a register now approaching sixteen million issuances, and the specific anomalies (ZC, NF, FC and the small alphanumeric ranges) that still trip up data pipelines built only for the unprefixed England-and-Wales case.

A number under section 1066

Section 1066(1) of the Companies Act 2006 is the bare statutory hook: "The registrar shall allocate to every company a number, to be known as the company's registered number." Subsection (2) lets the registrar specify the form — alphanumeric, fixed-length, with such prefixes as the registrar considers appropriate — and subsection (3) makes the number changeable only by direction of the registrar, which in practice almost never happens.

A few consequences follow from that minimal statutory frame:

• The number is issued at incorporation and survives re-registration. A private company that re-registers as public under section 90 keeps its number; only the suffix on the name (Ltd → plc) changes.
• The number is independent of the name. Companies House has processed more than four million name-change filings since 2006; not one moves a number.
• The number is independent of registered office. Moving from England to Scotland is not, in fact, possible under current statute (jurisdiction is fixed at incorporation), but moving address within a jurisdiction leaves the number unaffected.
• The number is unique across the register's lifetime. Numbers belonging to dissolved companies are not reused. If they were, the bona vacantia rules and the restoration mechanic (sections 1024–1034 CA 2006) would collapse.

That last point matters more than it sounds. A dissolved company restored to the register comes back with its original number. There is no "old" and "new" identity to reconcile; provenance is preserved.

The jurisdiction and entity-type prefixes

Under section 1066(2), the registrar uses a small set of prefixes to distinguish where and how an entity was incorporated. The table below captures the prefixes most likely to show up in a modern register search — those used for live filings as of 2026 — together with the Act under which the entity was first incorporated and the approximate share of the active register each occupies.

Three things to notice. The unprefixed England-and-Wales companies dominate so heavily that many third-party APIs are silently built on the assumption that a "company number" is eight digits with no letters. Anything alphanumeric is then either rejected at validation or coerced to digits, with predictable consequences for Scottish and LLP coverage. Second, the LP prefixes are easy to miss: there is no separate limited-partnership data product at Companies House — LP filings sit under the unified register — so an analyst filtering on entity type by number prefix is doing work the bulk product does not do for them. Third, the FC and BR distinction is the one that catches even careful drafters. An FC number identifies a foreign legal entity that has registered presence; a BR number identifies the UK establishment of that entity. The same underlying business can carry both.

What the prefix changes — and what it doesn't

The prefix is jurisdictional, not statutory. Sections 30 (entrenched articles), 168 (director removal by ordinary resolution), 540 (share capital) and the vast majority of the 2006 Act apply identically to a company numbered 12345678 and one numbered SC123456. What the prefix actually fixes is:

• The registry of incorporation (Cardiff, Edinburgh or Belfast). Filings are routed to the relevant office, although since the move to a unified online front-end all UK filings share the same submission infrastructure.
• The language obligations. Welsh-jurisdiction companies (registered in Cardiff with a Welsh-language name) may file in Welsh under section 1104; Scottish companies file in English; Northern Ireland filings sit under the Companies (Northern Ireland) Order regime, harmonised with CA 2006 since 2009.
• The gazette of record for statutory notice — the London, Edinburgh and Belfast Gazettes each handle their own jurisdiction.
• The insolvency court of first instance — the Court of Session in Edinburgh for SC numbers, the High Court of Northern Ireland for NI, the High Court of Justice in London for the rest.

What the prefix does not tell you:

• Whether the company is dormant. The AA02 filing pattern is independent of jurisdiction.
• Whether the company is audit-exempt. The April 2025 threshold uplift applies equally across the three jurisdictions.
• Whether the company has a PSC declaration on file. Part 21A applies to all UK companies and LLPs regardless of prefix.
• Whether the company is a CIC. Community Interest Companies are companies first; their CIC status is signalled by the suffix on the name and by the CIC34 community-benefit report, not by anything in the number.

The sequence: from 1844 to sixteen million

The English register, the oldest, began under the Joint Stock Companies Act 1844 and was consolidated under the Companies Act 1862. Companies House has now issued more than sixteen million unprefixed numbers since that Victorian start, of which roughly five million remain live and the rest are dissolved, struck-off or otherwise removed.

The sequence is monotonic but emphatically not linear in time. The first hundred thousand numbers took roughly the rest of the nineteenth century to issue; one million was reached around the mid-1960s; four million around the turn of the millennium; ten million around 2017; sixteen million in 2026. The acceleration since the 1990s tracks the spread of cheap online incorporation — the £12 software-channel fee that ran from 2016 to 2024 sat directly behind the rise — and is the structural reason ECCTA's identity-verification regime arrives now rather than a decade earlier.

A rough rule of thumb for ageing an unprefixed company from its number alone:

1. Numbers below 50,000 — Victorian incorporations, almost all dissolved, a handful of restored survivors.
2. 50,000–500,000 — 1900 to roughly 1960; older industrial and trading companies.
3. 500,000–2,000,000 — 1960 to 1989; the post-war small-company expansion.
4. 2,000,000–5,000,000 — 1990 to early 2000s; the close-company and dot-com-era boom.
5. 5,000,000–10,000,000 — 2003 to roughly 2017; online incorporations and the PSC-era onboarding.
6. 10,000,000+ — post-2017; many of these are the formations now under most scrutiny in ECCTA's verification rollout.

That rule breaks at the SC and NI sequences, which are much shorter (Scottish numbers sit in the high six figures, NI numbers around 700,000) and at the OC sequence, which started at OC300000 in April 2001 when LLPs went live. An LLP number below OC400000 is almost certainly more than fifteen years old; an LLP number above OC450000 is a recent vintage.

Anomalies: ZC, NF and the ranges that confuse APIs

Beyond the live-issuance prefixes, the register holds historical numbers that catch out anyone parsing in volume. The most common:

• ZC numbers identify pre-1856 unregistered companies — bodies that pre-date statutory registration and that filed under various transition provisions. There are fewer than a thousand active.
• NF is used for certain Northern Ireland companies that pre-date the 1986 Order regime and were re-papered into the unified register.
• AC and NA ranges cover former assurance and guarantee structures, mostly historical.
• CE marked UK Societas (and the earlier SE) registrations; with the Societas Europaea now removed from the UK legal palette post-Brexit, CE and SE numbers persist on the register only as dormant or in-conversion records.
• IP, SP, NP — Industrial and Provident Society numbers — are not Companies House numbers at all; they are issued by the FCA's Mutuals Public Register. Pipelines that scrape both registers in parallel and concatenate on "registration number" will collide.

A practical implication: any internal system that validates a company number with the regular expression ^[0-9]{8}$ will silently reject every Scottish company, every LLP and every overseas branch on the register. The Companies House public API itself accepts the alphanumeric form; the bulk product returns it as-is. Validation tightened too far is the second most common cause of jurisdictional under-coverage in third-party data, after API quota throttling.

ECCTA, the verified registry and the number's continuing role

ECCTA 2023 has not amended section 1066. The number system is one of the few features of the 2006 Act that the reform programme has left structurally untouched, even as identity verification, ACSP supervision, appropriate-address standards and the lawful-purpose declaration have been bolted on around it. The number remains the registrar's primary key, and the new verification metadata hangs off it: directors and PSCs are tied to companies by number, not by name.

For due diligence, this means the number now acts as the join key between the live filing record and the new verification layer — the same eight characters that have appeared on every incorporation certificate since the 1860s.

Reading a number in practice

The shortest checklist for an analyst handed an unknown number:

1. Prefix → jurisdiction and entity type (use the table above).
2. Sequence range → vintage (decade of incorporation, within tolerance).
3. Resolve on Companies House Service for the name and filing record — confirm the prefix and number return a single, current entity.
4. Cross-check against the Charges Register (MR01 history), the disqualified directors register and, where applicable, the Register of Overseas Entities — each of which uses the Companies House number as its primary join key.
5. Compare the number against the stated date of incorporation. A wildly mismatched pair (a recent number with a 1990s incorporation date, or vice versa) is almost always the registrar correcting a historic re-registration: rare, but worth investigating before you rely on the filing record at face value.

Eight characters of provenance; one statutory hook in section 1066; one hundred and sixty-four years of issuance. The number is the least glamorous datum in any Companies House search result, and quietly the most reliable.