| LEI | 20-character code for the company, standard ISO 17442 |
| Who issues LEIs | LEI issuers (local operating units), plus over 100 registration agents |
| ISIN | identifier of the security, standard ISO 6166 |
| Who issues ISINs in the UK | London Stock Exchange as national numbering agency, prefixes GB, GG, IM, JE |
| ISIN cost at the LSE | no fee for allocation or maintenance |
| Updated | November 2026 |
What an LEI is
The LEI (Legal Entity Identifier) is a 20-character alphanumeric code that identifies exactly one company, uniquely, worldwide. It rests on the international standard ISO 17442 and the system is run by GLEIF, a not-for-profit foundation backed by the G20 and the Financial Stability Board.
Behind every LEI sits verified reference data from official sources, including the ownership structure. The Global LEI Index thereby answers who is who and who owns whom. The data is a public good and free for anyone to look up. For a PLC this means: what the LEI says must match what Companies House says, or the mismatch will surface at the first bank or broker at the latest.
Who issues an LEI, and how the application works
LEIs are issued by LEI issuers, also called local operating units (LOUs). They handle registration, validation and renewal, and they are a company's first port of call. On top of that, more than 100 registration agents help companies reach the LEI issuers. GLEIF keeps the list of all official bodies.
Who requires an LEI follows from the rules of your trading venue, your bank and your broker. When we prepare a listing, it goes on our checklist as soon as the company has its final shape. How the listing works as a whole is described on the PLC going public page.
One tip from practice: keep the renewal in the calendar. An LEI whose data is no longer confirmed still exists, but to a bank that looks closely it is a warning sign.
What an ISIN is and who issues it in the UK
The ISIN (International Securities Identification Number) identifies not the company but the individual security, for example your PLC's ordinary shares. It follows the ISO 6166 standard. Valid ISINs are issued only by the official national numbering agencies.
For the United Kingdom, Jersey, Guernsey and the Isle of Man that is the London Stock Exchange. It issues ISINs with the prefixes GB, GG, IM and JE, along with the CFI code (the security's classification) and the FISN (its short name). An ISIN starting with GB therefore belongs to a security allocated through that agency.
And now the good news: the London Stock Exchange charges no fee for allocating an ISIN, and none for maintaining it.
ANNA, the association of national numbering agencies, expressly warns about third parties that charge for obtaining or supposedly maintaining an ISIN and threaten to have a valid ISIN removed from systems otherwise. Treat such demands with scepticism. Apply for the ISIN directly at the official agency.
How to apply for an ISIN at the London Stock Exchange
The application is made online. This is how it looks when we prepare it for a PLC.
- 1
Fix the core data
Name, registered number, registered office, share class and nominal value must match Companies House and the articles.
- 2
Open a UnaVista account
Before the first application you need a free user account with UnaVista. Registration is needed only once.
- 3
Apply through Pegasus
All UK ISIN applications go through Pegasus Online ISIN Submission. The applicant confirms that they are authorised to act for the issuer and that the details are correct.
- 4
Number into the register and the documents
The ISIN goes into the register of members, the admission documents and announcements, so that everyone involved uses the same number.
LEI, ISIN and running the PLC
Neither number is an end in itself. They connect the company to the world of banks, brokers and trading venues. For that to work, the registers, articles and Companies House filings must be clean. That is the real work, and the part we take care of. How the shares themselves will in future be held only electronically is covered under dematerialisation.
Common questions about LEI and ISIN
What is an LEI number?
A 20-character code under ISO 17442 that identifies a company uniquely worldwide and is linked to verified reference data.
Where do I apply for an LEI?
At an LEI issuer (local operating unit) or through a registration agent. GLEIF keeps the official list.
What does an ISIN cost in the UK?
Nothing at the London Stock Exchange: no fee for allocation and none for maintenance.
What does GB at the start of an ISIN mean?
It is the country prefix of the issuing agency. The London Stock Exchange issues ISINs with the prefixes GB, GG, IM and JE.
Sources: GLEIF: Introducing the Legal Entity Identifier (LEI); GLEIF: Get an LEI, find LEI issuing organizations; LSEG: ISIN Services
