Searching for “CRO UK” can lead to the wrong register. The Companies Registration Office (CRO) is the company registrar for the Republic of Ireland. Companies House is the UK registrar, including for companies incorporated in Northern Ireland. The correct starting point is where the legal entity was incorporated, not where its customers live, its website ends or its directors are based.
Direct answer
Use CRO CORE for companies incorporated in the Republic of Ireland and Companies House for UK-incorporated companies, including Northern Ireland. A business can also have a registered branch or establishment across the border, so check both registers when it specifically claims one. An ordinary cross-border sale does not, by itself, require two company registrations.
There is no UK Companies Registration Office equivalent called the CRO
“CRO” in an Irish company-search context means the Republic of Ireland’s Companies Registration Office. The UK’s public corporate registrar is Companies House. This matters because a query for an “Irish CRO number” in a UK-only search can return no result even though the Irish company exists. Similarly, an Irish CRO search is not the correct way to find a company incorporated in Belfast, London, Cardiff or Edinburgh.
Sometimes a UK business uses “CRO” for something unrelated to the Irish company register. Look at the document or website around the acronym before assuming it means a company number. If you are checking a legal company, ask for its incorporation jurisdiction and company registration number; these identify the record more reliably than a brand name.
CRO Ireland vs Companies House UK at a glance
| Question | Irish CRO | UK Companies House |
|---|---|---|
| Which jurisdiction? | Republic of Ireland | United Kingdom, including Northern Ireland |
| Official company search | CORE entity search | Find and update company information |
| Search inputs | Entity name or register number | Company name, number or officer name |
| Typical public evidence | Irish company identity and available CRO filings | UK identity, officers, filings and document images |
| Cross-border presence | May show a registered Irish branch of an external company | May show a UK establishment of an overseas company |
| What a result is not | A trading, credit or trustworthiness guarantee | A trading, credit or trustworthiness guarantee |
Public record types and filing rules are not identical. Do not compare two companies merely by asking whether they have the same-looking document or status label. Use the company number, filing period and applicable register to interpret each item.
Republic of Ireland or Northern Ireland?
This is the most common geographic trap. The Republic of Ireland and Northern Ireland share an island but not a company registrar. A company incorporated in Northern Ireland is a UK company on Companies House. A company incorporated in Dublin, Cork or Galway is on the Irish CRO. A postal address can be a clue, but a group may have offices on both sides of the border. The legal name and registration number on the contract decide which entity you are investigating.
If a Northern Ireland company supplies customers in the Republic, do not expect it to be incorporated a second time in Ireland. If it has established a registrable Irish branch, the CRO may also hold a branch record. CRO guidance says an external company establishing a branch in the State must register under Part 21 of the Companies Act 2014; that is a separate question from simply selling goods or services to Irish customers.
What if an Irish company has a UK branch?
Companies House guidance says an overseas company generally registers a UK establishment when it sets up a place of business or branch with physical presence in the UK. It also explains that carrying on business with UK customers alone does not automatically create that requirement. An Irish company with a registered UK establishment should therefore be checked in both places: the Irish CRO for the incorporated company, and Companies House for the UK establishment and its filings.
Do not confuse the establishment with a separately incorporated UK subsidiary. A branch is part of the foreign company; a subsidiary is a distinct legal company with its own incorporation. Our Irish branch versus subsidiary guide gives the structural differences. If the counterparty’s invoice names the subsidiary, research that entity even if the parent brand is better known.
What if a UK company has an Irish branch?
The reverse can also happen. The UK company’s primary record remains with Companies House, while a registered Irish branch appears at the CRO. Look for the relationship between the records and compare the exact name on your agreement. The CRO’s external-company guidance sets out registration rules for foreign companies establishing branches in Ireland. A branch number should not be mistaken for an Irish-incorporated subsidiary’s own company number.
A business can also use a trading name without creating a new company. One group may have a UK parent, an Irish subsidiary and several brands. Draw a simple map of the actual contracting entity, parent and branch before making a credit or payment decision. Similar names across registers are clues to investigate, not proof of control or liability.
How to check a cross-border company step by step
- Read the contract or invoice and write down the full legal name, company number and registered jurisdiction.
- Search the incorporation register: Irish CORE or UK Companies House.
- Compare the registered status, office, incorporation date and available filings with the supplier’s claims.
- If a branch or UK establishment is claimed, search the second register and establish how that record relates to the home company.
- Confirm the person contacting you and the receiving bank account through independent channels.
- Keep the records and dates of both searches; recheck them before a high-value transaction.
For a Republic of Ireland company, you can start with a Businesses.ie company search and open the same record at CORE for official confirmation. Our focused guide to searching an Irish CRO company from the UK includes the supplier and payment checks that follow the initial lookup.
Which number should you put in each search box?
Use an Irish CRO number in an Irish company search and a UK company number in Companies House. A VAT number, EORI number, charity number or branch identifier may serve a different administrative purpose and should not be substituted for the incorporation number. Ask the supplier to label each identifier rather than guessing from the length or prefix. Names are especially risky where a UK and an Irish company share a near-identical brand.
For an invoice, the VAT number needs its own check. GOV.UK provides a UK VAT-number checker; it does not find a VAT number from a business name. A valid VAT result cannot authenticate an emailed request to change bank details. Keep tax, company identity and payment verification as separate tasks.
Can either register tell you the company is safe?
No. Both registers publish information companies are required to file, but a search result is not a government recommendation, a credit score or proof that the business currently delivers goods. A fraudster may copy a genuine company’s number into a fake website or invoice. Old accounts may not reflect this month’s trading position. Review material filings, verify the contact independently, and request up-to-date evidence where the commercial exposure warrants it.
If you need to know whether an Irish entity is actively trading, read our trading-status evidence guide. For an incorporated Irish customer or supplier, a company report can help organise the public CRO record into a review, but it cannot replace direct confirmation of a contract, licence or bank account.
Sources and editorial review
Reviewed on 22 September 2026 against CRO guidance on CORE entity search and external companies, plus Companies House guidance on UK company information and overseas companies with UK establishments. This is general register-navigation guidance, not legal or tax advice.