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Category — Issue Parameters
By Konstantin Vasilev Member of the Board of Directors of Cbonds, Ph.D. in Economics
Updated August 06, 2023

What is ISIN?

The 12-digit alphanumeric code known as an International Securities Identification Number (ISIN) is a code that serves to identify securities. Each country has its own National Numbering Agency (NNA), responsible for allocating ISINs within its jurisdiction.

The first two characters of an International Securities Identification Number (ISIN) indicate the Country of Quotation, representing the geographical origin of the security. However, it’s important to note that these characters identify the issuer’s country of origin and not that of the underlying issue. To ensure consistency, these characters must adhere to the ISO 3166-1 standard by the International Organization for Standardization, which is widely used for denoting places. For instance, "IT" corresponds to Italy, "DE" to Germany, "US" to the United States, "FR" to France, and so forth. Eurobonds registered by Euroclear and Clearstream are an exception, as they have the letters "XS" as a prefix, an internationally accepted convention for quickly identifying Eurobonds. For instance, even though a Eurobond issuer (e.g., BMW) may be based in Germany, its ISIN code may start with "XS."

The next 9 characters, or from the third to the eleventh character, are called the National Securities Identifying Number (NSIN). The NSIN is assigned by each country’s National Numbering Agency. In Germany, for example, the assigning company is WM Datenservice and the NSIN is Wertpapierkennnummer; in the United Kingdom, the assigning company is the London Stock Exchange and the NSIN is SEDOL; in Italy the assigning agency is the Bank of Italy; in France - Euronext and in North America CUSIP is used as NSIN. Where the NSIN consists of fewer than 9 characters, zeros are inserted in front of the number to make up the nine characters.

Finally, the last character, or the twelfth, is a Check Digit. This number is a form of redundancy check used for error detection. It is calculated according to the previous 11 characters and performs two functions: it prevents the risk of counterfeit numbers and confirms the authenticity of the code itself. Generally, the Check Digit is designed to cope with any typing errors of human operators.


History of ISINs

The global adoption of International Securities Identification Numbers (ISINs) recognized by the International Organization for Standardization, facilitates seamless trade clearing and settlement through Global Straight-Through Processing (GSTP), an electronic process. ISINs serve as a consistent format for tracking the holdings of institutional investors across worldwide markets.

Initially introduced in 1981, ISINs gained widespread acceptance in 1989 following a recommendation from G30 countries. The International Organization for Standardization (ISO), officially endorsed ISINs a year later, in 1990.

Each country’s relevant National Numbering Agency (NNA), a financial institution responsible for issuing ISINs, is in charge of assigning these internationally recognized codes. In the United States, the CUSIP Service Bureau, part of CUSIP Global Services, serves as the National Numbering Agency and plays a vital role in establishing country-wide standards for the financial services industry. In the US, ISINs are extended versions of 9-character CUSIP numbers, with a two-digit country code added at the beginning and an additional check digit appended at the end to ensure accuracy.

The structure of ISINs is defined by ISO 6166, and these unique alphanumeric characters can be assigned to various types of securities, including debt instruments such as bonds, commercial paper, stripped coupons, T-bills, and more. ISIN numbers are universally recognized and play a crucial role in regulatory reporting, settlement purposes, and other numerous reasons within the global financial landscape.

By providing a standardized and universally recognized code, ISINs serve as a vital tool for identifying securities and supporting efficient trade processes across international markets.

How ISINs work

The primary purpose of the ISIN code, recognized by the International Organization for Standardization (ISO), is straightforward - it provides a simple identification mechanism, without implying responsibility for the actual existence, legitimacy, or validity of the financial instrument by the National Numbering Agency (NNA). Moreover, the ISIN coding system does not encompass information about the issuer’s financial solidity or the security’s coverage. Instead, ISIN ensures a consistent and comparable format for all securities and financial instruments globally, allowing easy and clear identification, and enabling institutional investors to monitor these securities worldwide.

Due to its unique nature, an ISIN code, consisting of 12 characters, cannot be assigned to multiple securities, even if they share similar characteristics. Each separate security, such as bonds, warrants, and debt securities, will have its distinct ISIN code.

It’s essential not to confuse the ISIN code, a universally recognized identifier, with the Ticker symbol, a three-letter exchange code that identifies stocks at the stock exchange level. A company’s stocks may have multiple ticker symbols on different trading platforms, but they will always have only one ISIN.

As a unique and universal code, the ISIN, assigned by relevant National Numbering Agencies, provides the fastest and safest way to access necessary information about a security. It is now possible to search for a financial instrument using its ISIN code on any trading platform, international stock exchange, or specialized site, like the London Stock Exchange.

Increasingly, more countries, including those in the European Union, are adopting the ISIN as a standard for classifying their securities in circulation. This is critical to achieving global straight-through processing (STP), which involves digital management of clearing and settlement activities without manual intervention, benefiting both investors and markets. Moreover, certain regulations, like Solvency II, now require the use of ISIN codes to identify and standardize all securities, including warrants, in the market.


Here are the revised ISIN examples for a US company’s stock certificate and a theoretical Namibian company:

  1. US company’s stock certificate: US0004026250

  2. Theoretical Namibian company: NA000K0VF054


CUSIP is a standard comprising nine digits utilized solely for identifying securities issued in the United States and Canada. Conversely, ISIN is a global standard, employing twelve characters to uniquely identify any security issued anywhere in the world.

The CUSIP code is almost a mirror image of the ISIN code itself. In fact, its structure is based on CUSIP codes. For example: 21st Century Fox America, 3% 15sep2022, USD, here it can be seen that the ISIN code of the Eurobond is US90131HAR66, and its CUSIP code is 90131HAR6. That is, the CUSIP code corresponds to the third to the eleventh characters of the ISIN code. Therefore, it can be said that the ISIN code is based on the structure of a CUSIP with the addition in principle of the two characters indicating the geographical origin of the issuer and the last character.

ISIN vs. Ticker symbol

A stock ticker is a concise abbreviation for specific stocks or securities listed in exchange order books, often limited to three letters or fewer. On the other hand, an ISIN is a distinctive twelve-digit code that serves as a unique identifier for any public security worldwide. Unlike ISINs, ticker symbols lack uniqueness: a single company may have different ticker symbols on various exchanges where it trades, and two distinct companies can use the same ticker symbol if they operate in different markets. However, a particular security can only be associated with one ISIN, and vice versa.


  • What does ISIN tell you?

  • Do all companies have an ISIN?

  • Do all securities require an ISIN number?

  • How many digits does an ISIN have?

  • What are the requirements for an ISIN number?

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