A UK company's registered office is the address the law makes it keep for legal post. It is often not where the company works. Formation agents, virtual-office providers, accountants and solicitors all supply registered offices, and the free Companies House data product has no column for a trading address at all. So when a supplier, customer or applicant hands you "the company address", you are usually holding a service address, and the useful question is what kind.
The general picture — a mailbox branch, an agent's office and a crowded building are three different things, and mail_drop_source says which one Spaw found — is in a registered agent's address is not a mail drop, and not a home. This guide covers what the UK adds to it: a legal test for registered offices since March 2024, an address the registrar keeps for companies that fail that test, and counts from the register itself.
Every count below comes from the Companies House free company data product, the BasicCompanyData snapshot dated 1 September 2026, read in full on 22 September 2026. The snapshot lists 5,689,367 companies. None of them is dissolved: a struck-off company leaves the file rather than being marked.
The rule since 4 March 2024: an "appropriate address"
The Economic Crime and Corporate Transparency Act 2023 rewrote section 86 of the Companies Act 2006, with effect from 4 March 2024. A company must keep its registered office "at all times at an appropriate address", and an address qualifies if, in the ordinary course of events, "a document addressed to the company, and delivered there by hand or by post, would be expected to come to the attention of a person acting on behalf of the company" and "the delivery of documents there is capable of being recorded by the obtaining of an acknowledgement of delivery" (https://www.legislation.gov.uk/ukpga/2006/46/section/86, accessed 22 September 2026).
The government's guidance puts it more bluntly: "You can no longer use a Royal Mail PO Box as your registered office address. This includes similar services from other companies." It adds that a service provider's address, such as an accountant's or solicitor's, "must meet all of these requirements" (https://www.gov.uk/limited-company-formation/company-address, accessed 22 September 2026).
Notice what the rule does not say. It does not ban formation agents or virtual offices. An agent's building where somebody signs for the post and acts for the company can be an appropriate address, and a company registered there has done what the law asks. What the rule rules out is a box on its own.
The Companies House default address
Anyone who believes a company's registered office is not appropriate can ask the registrar to change it, on form RP07. If satisfied, the registrar may move the registered office to "what is known as a default address. This is an address held and maintained at Companies House (the default address used will depend on the company's jurisdiction)" (Registrar of Companies: rules and powers, https://www.gov.uk/government/publications/company-registrars-rules-and-powers/company-registrars-rules-and-powers, updated 4 March 2024, accessed 22 September 2026). The same page says what happens next. The company has 28 days to file a new address, with evidence that it may use the property. After that the registrar may publish a notice of intention to strike it off, and after two more months strike it off. Meanwhile the registrar is not required to open the post that arrives, and may destroy anything uncollected after six months.
The guidance cited here does not print the default addresses; the register does, in every record moved there. Each is written as a Companies House PO box, then the company number and the words "Companies House Default Address". In the 1 September 2026 snapshot, 28,936 companies have a registered office written that way:
| Default address | Company numbers there | Companies |
|---|---|---|
| PO Box 4385, Cardiff CF14 8LH | England and Wales | 27,456 |
| PO Box 24238, Edinburgh EH7 9HR | Scotland | 934 |
| PO Box 2381, Belfast BT1 9DY | Northern Ireland | 546 |
How it was counted: each row's care-of, PO box, first and second address lines and post town were joined and searched for the words "DEFAULT ADDRESS"; the postcode is the row's own RegAddress.PostCode; the jurisdiction is read from the company number prefix: SC and SO numbers are Scottish, NI numbers Northern Irish, and the Cardiff box holds the rest — 27,295 plain numbers, 152 OC and 7 LP, the England and Wales series, plus one FC and one GE. Three more rows carry the Cardiff postcode without those words, and they are not counted.
Of the 28,936, 22,640 (78 percent) have the status "Active - Proposal to Strike off", 820 are in liquidation and 5,410 are plainly "Active". That is the rule working as the registrar's page describes it: a company that does not replace the default address is heading off the register. How a UK dissolution shows up in open data covers what that looks like afterwards.
Written the way the register writes it, each default address is a post-office box with no street, and Spaw reads it as one: address_type: po_box. A box has no building behind it, so no register of buildings is asked and companies_registered stays null. What else the answer carries depends on the postcode:
- Edinburgh, EH7 9HR is a live postcode, so the box is the only signal: the
po_boxweight of 30, and a risk score of 30. - Cardiff, CF14 8LH also carries
terminated_postcode, another 30, for a score of 60. The ONS Postcode Directory's August 2026 release records CF14 8LH as terminated in March 2016; the register still prints it for 27,456 companies. - Belfast, BT1 9DY answers
postcode_status: null: not evaluated, rather than live or terminated. Northern Irish postcodes are left out of the directory installed here, because their reuse needs a Land & Property Services licence, so the code is neither confirmed nor refused and carries no centroid. The box is again the only signal, for a risk score of 30. Can you look up UK addresses from a postcode for free? explains the gap.
The PO box column
The snapshot also has a RegAddress.POBox column, and 31,145 companies have a value in it. Read carelessly, that looks like thirty-one thousand companies breaking the box rule. It is not. 28,921 of those values are the registrar's own box numbers at the three default addresses. The other 2,224 hold some other box, and all but one of them also give a first address line. A box number next to a street address does not tell you whether the street address is appropriate, so the column cannot settle that question.
What each open source can and cannot say
Spaw's is_mail_drop flag for a UK address comes from three sources, reported in mail_drop_source in this order of precedence:
| Source | What it can say | What it cannot say |
|---|---|---|
operator_list: Mail Boxes Etc's own centre pages |
The address is a Mail Boxes Etc centre, where anyone can rent a mailbox. The pages crawled on 16 September 2026 list 124 UK centres (115 in England, 6 in Scotland, 2 in Northern Ireland, 1 in Wales) and 4 in Ireland; 121 of the 124 key to a building. | Which companies or people rent a box there; other operators' centres; a centre opened since the crawl. |
registered_agent: the bundled agent list |
The address is one a formation or registered-office service publishes, or one that Companies House filings naming the service carry, and mail_drop_provider names the service. In the list's 16 September 2026 version, 8 of its 17 agents have a British address: 2 checked against the agent's own site, 6 against Companies House filings that name the service. |
Which companies use the agent; whether any of them trades there; agents the list does not hold. |
company_cluster: Companies House counts |
At least 25 companies — the published threshold — name the building as their registered office, and companies_registered carries the count. |
Why: a formation agent the list does not know, an accountant's office, a serviced office and a large landlord all look the same. A building below the threshold is not flagged. |
Two more counts from the same snapshot, keyed on 23 September 2026 the way the lookup keys an address (a house number, a street and a postcode or town, folded to one key per building), show why the threshold matters. 4,109,723 companies have a registered office that keys to a building, across 1,838,998 buildings. 10,460 of those buildings carry 25 companies or more, and between them they hold 1,541,045 companies: 37 percent of every company that keyed. A hundred and one buildings carry a thousand or more. These are counts per building across the whole register; the British postcode district pages tally the same snapshot district by district, keyed by district rather than by building, so a sum of their counts need not match these.
The lists and the count overlap. Of the 121 Mail Boxes Etc centres that key, 78 stand at a building with 25 or more companies registered, so the count alone would flag them. The list is what names the operator, and what catches the other 43.
Telling the trading address apart
- Treat the registered office as a service address. The register records a registered office, not a trading address, and a formation agent's office is a lawful registered office. Ask for the trading address separately, and say why.
- Read the source, not just the flag.
registered_agentis the most ordinary answer a registered office can give.operator_liston a registered office invites a question: is post going to a rented box?company_clusteris a count to read. - A trading address should answer none of the three. It is also no box: an address that reads as
po_boxorprivate_mailboxis a place post is collected, not a place business is done. What a PMB (private mailbox) is, and why it cannot prove where you live covers the second. - A default address is a warning about the record, not the company's trade. The registrar moved the registered office there, and most such companies are on their way off the register.
A mail drop is not a "drop address"
The two phrases sound alike and mean different things. A mail drop, in Spaw's answer, is a fact about a place: the address takes post for companies and people who are not there. In parcel-fraud slang, a "drop address" is how one order uses an address. Goods bought with stolen payment details go to an address where someone — a mule, in fraud teams' vocabulary — collects or reships them. It can be anyone's home, and nothing about the building marks it: no branch list or company count would flag it.
Spaw holds no list of reshippers or parcel mules, and is_mail_drop is not built to detect that fraud and does not. A checkout that wants to act on the delivery-point facts Spaw does hold can do so through the shipping policy.
None of this says anything about a person
Every number in this guide counts companies on a public register. Every flag is a fact about a building: who publishes it as a branch, whose office it is, how many companies name it. None of it says who lives or works at an address, whether a company registered at an agent's office is honest, or why a company ended up at the default address. The response carries no field that says who is anywhere. For the fields themselves, see the address verification guide, and try any address on the free postal address checker.