Business Registration Number: What It Is Called by Country

A business registration number is the number a public register gives a company when it is formed.

Only one of the six jurisdictions below prints those exact words on a certificate, and there the number comes from the tax office.

The short answer

Three things to hold on to:

• The phrase on the form is generic. The number that answers it is local.
• In Estonia, Singapore and Hong Kong, the same number also serves the tax office.
• In the United Kingdom, Ireland and the United States, the tax number is a separate one.

What the phrase means

"Business registration number" is a question on a form, not the name of a number. Forms ask it under several labels:

• business registration number
• company registration number
• company number
• registration number or registry code

All four point to the same thing: the identifier a register assigned when the company was created. It answers one question, which is whether this legal entity exists and which one it is.

United Kingdom: company number

012345678 characters, Companies House

Hong Kong: Business Registration Number

123456788 digits, Inland Revenue Department

Also stands in as the tax identifier.

Singapore: Unique Entity Number

202412345X10 characters, ACRA

Also the tax identifier.

Ireland: CRO number

123456up to 6 digits, Companies Registration Office

Estonia: registry code

123456788 digits, Business Register

Also the tax identifier.

Delaware: file number

12345677 digits, Division of Corporations

Example numbers show the shape only. In the United Kingdom, Ireland and the United States the tax number is a separate one.

The form asks one question. The answer has a different name, a different issuer and a different shape in each country, so the country comes first and the number second.

This page covers the six jurisdictions we work in. Three kinds of identifier are out of scope:

• registration numbers of other countries
• tax numbers, which get their own section below
• global codes such as the LEI or a DUNS number, which are not national register numbers

United Kingdom: the company number

• Official name: company number, also written company registration number
• Issued by: Companies House
• Shape: always eight characters, such as 01234567
• Where to read it: the certificate of incorporation, or the public register, which is free

The leading zero in the example is part of the number, not formatting. That single point causes most rejected forms, and it has its own guide: how prefixes and leading zeros work in a UK company number.

Hong Kong: the Business Registration Number

• Official name: Business Registration Number, or BRN
• Issued by: the Inland Revenue Department
• Shape: eight digits, such as 12345678
• Where to read it: the Business Registration Certificate, which the business must display

Hong Kong is the one place where the generic phrase is also the official name. It is also where the count of numbers depends on a date:

• A company formed on or after 27 December 2023 has the BRN only.
• An older company also keeps a 7 digit company number from the Companies Registry.

The detail is in the one-number rule for Hong Kong companies formed since 2023.

Singapore: the Unique Entity Number

• Official name: Unique Entity Number, or UEN
• Issued by: ACRA for companies, and other agencies for some entity types
• Shape: ten characters for a local company, such as 202412345X
• Where to read it: a BizFile search by name, free, or the company's invoices

Singapore gives each entity one number, and every government agency uses it. The number is not opaque either: the example above opens with the year of registration. Our guide explains how to read the year and the entity type in a UEN.

Ireland: the CRO number

• Official name: CRO number, also called company number
• Issued by: the Companies Registration Office, at incorporation
• Shape: up to six digits, no letters, such as 123456
• Where to read it: the certificate of incorporation, or CORE, the CRO's free online portal

A number with a letter prefix is not the CRO number. An Irish company carries several identifiers, and only this one is fully public and permanent. See the four Irish numbers and which one a form wants.

Estonia: the registry code

• Official name: registry code, in Estonian registrikood
• Issued by: the Estonian Business Register, automatically at registration
• Shape: exactly eight digits, no letters, such as 12345678
• Where to read it: the company's entry in the e-Business Register, free for basic data

Estonian business practice also puts the code on invoices and contracts. The usual mistake is to hand over the VAT number instead, which is a different number from a different body. The guide covers what the registrikood is, and what it is not.

Delaware: the file number

• Official name: file number
• Issued by: the Delaware Division of Corporations, at formation
• Shape: seven digits, no prefix, such as 1234567
• Where to read it: the stamped Certificate of Formation, or the state's public entity search

This is a state identifier. It proves the company exists in Delaware, and it identifies the company in Delaware's register. Two consequences for a foreign form:

• Each US state assigns its own number to the entities it registers.
• The federal number a company carries is the EIN, which is a tax number.

The split is explained in which request wants the file number and which wants the EIN.

Is it also the tax number?

Most guides say the registration number and the tax number are always two different things. For three of these six jurisdictions, that is wrong.

Two cautions before you copy a number across:

• A VAT number is a third identifier. In Estonia it is EE plus nine digits, and it is not the registry code.
• A shared number does not prove a tax status. In Singapore, GST registration is a separate check.

Which number goes in a "TIN" box, form by form, is the subject of our tax identification number guide.

What a foreign form wants from your company

A form drafted abroad rarely uses your register's vocabulary. Translate the label first, then write the number.

Four habits prevent most rejections:

1. Read the country field before the number field.
2. Type the number as text, so that zeros and letters survive.
3. Give the tax number only when the label says tax.
4. Check the number against the certificate before you send it.

One rule of thumb from the Delaware case travels well. A request about the company's existence wants the registration number. A request about money moving or tax being reported wants the tax number.

About the company's existence

Registration number

Which legal entity is this, and does it exist?

• Company number, BRN, UEN, CRO number, registry code, file number
• Read on the certificate or the public register

About money or tax

Tax number

Give it only when the label says tax.

• Separate in the UK (UTR), Ireland (TRN) and the US (EIN)
• The same number in Estonia and Singapore, in effect in Hong Kong

Where the number is printed

Two sources work in every jurisdiction: a document issued to the company and the register itself.

Some jurisdictions also oblige the company to show the number:

• United Kingdom: on business letters, order forms and the website.
• Ireland: on business letters and the website.
• Hong Kong: the valid Business Registration Certificate is displayed at the place of business.
• Singapore: on invoices.

How to search each register is covered in our register search guides, one per jurisdiction.

Does the number ever change?

The number outlives almost everything else about the company. Our country guides publish the following.

For the two others, our guides say less:

• Singapore: the UEN does not change with the company's name.
• Hong Kong: the BRN stays the same through certificate renewals.

That permanence gives the number its value in due diligence:

• A name can change, and the register keeps the number.
• A new number means a new legal entity, whatever the name suggests.
• A dissolved company that re-forms starts again with a new number.

The summary