# ISIN Key: `finance.securities.isin` International Securities Identification Number. 12-character alphanumeric code that uniquely identifies a specific securities issue. Format: 2-letter country code (ISO 3166-1) + 9-character alphanumeric NSIN + 1 check digit (Luhn on alpha-to-numeric conversion where A=10, B=11, ..., Z=35). Page: Samples: `US0378331005`, `GB0002634946`, `JP3633400001`, `DE0007164600` ## Background ### Origin An International Securities Identification Number (ISIN) is a code that uniquely identifies a security globally for the purposes of facilitating clearing, reporting and settlement of trades.[[1]](https://en.wikipedia.org/wiki/International_Securities_Identification_Number) The structure of the ISIN is defined in the international standard ISO 6166.[[1]](https://en.wikipedia.org/wiki/International_Securities_Identification_Number)[[2]](https://arthurdejong.org/python-stdnum/doc/2.2/stdnum.isin) ISINs were first used in 1981, but did not reach wide acceptance until 1989, when the G30 recommended their adoption.[[1]](https://en.wikipedia.org/wiki/International_Securities_Identification_Number) Wikipedia says ISO endorsed the ISIN with the ISO 6166 standard a year after the G30 recommendation.[[1]](https://en.wikipedia.org/wiki/International_Securities_Identification_Number) Wikipedia refers to the current text as ISO 6166:2021, from the 2021 revision of the standard.[[1]](https://en.wikipedia.org/wiki/International_Securities_Identification_Number) ISINs are allocated by National Numbering Agencies (NNAs), with the jurisdiction set by the assignment rule in the ISO 6166 standard.[[3]](https://anna-web.org/faq-page/) The Association of National Numbering Agencies (ANNA) is the registration authority for the ISIN.[[4]](https://www.gleif.org/en/lei-data/lei-mapping/download-isin-to-lei-relationship-files) Spain's CNMV says the need for cooperation between national agencies, to ensure that each ISIN is unique and that all ISINs are available to users, led to the creation of ANNA.[[5]](https://internet.cnmv.es/portal/ancv/anna?lang=en) ANNA was founded by 22 countries, including Spain, and held its first general assembly in London in February 1992.[[5]](https://internet.cnmv.es/portal/ancv/anna?lang=en) At the end of 2025, ANNA had 120 full member countries and 5 partners, which have limited rights within the association.[[5]](https://internet.cnmv.es/portal/ancv/anna?lang=en) ### Use An ISIN is always 12 characters long: two letters, nine alphanumeric characters and one numerical check digit.[[1]](https://en.wikipedia.org/wiki/International_Securities_Identification_Number) The nine middle characters are the National Securities Identifying Number (NSIN), padded as necessary with leading zeros.[[1]](https://en.wikipedia.org/wiki/International_Securities_Identification_Number) Wikipedia gives the check digit as calculated using the Luhn algorithm.[[1]](https://en.wikipedia.org/wiki/International_Securities_Identification_Number) Before the Luhn calculation, letters are converted to numbers by taking the ASCII code of the capital letter and subtracting 55, so U becomes 30 and S becomes 28.[[1]](https://en.wikipedia.org/wiki/International_Securities_Identification_Number) Apple's ISIN, US0378331005, is the CUSIP 037833100 with the country code US added at the front and a check digit at the end.[[1]](https://en.wikipedia.org/wiki/International_Securities_Identification_Number) CUSIP Global Services is responsible for the assignment of ISINs in the U.S.[[6]](https://www.cusip.com/identifiers.html) CUSIP Global Services says a CUSIP or CINS identifier will always appear in positions 3 to 11 of an ISIN it assigns.[[6]](https://www.cusip.com/identifiers.html) CUSIP Global Services summarises the ISO rule for an equity ISIN's country code as the country where the entity is incorporated.[[6]](https://www.cusip.com/identifiers.html) For international debt issues, CUSIP Global Services gives the country code as the country where the Central Securities Depository is located.[[6]](https://www.cusip.com/identifiers.html) An ISIN does not specify a particular trading location.[[1]](https://en.wikipedia.org/wiki/International_Securities_Identification_Number) Read the two leading letters as a clue to where the code was allocated, not as the security's listing venue or trading currency, and keep the exchange in a column of its own. (Meridian's view) When the NSIN changes due to corporate actions or other reasons, the ISIN changes too.[[1]](https://en.wikipedia.org/wiki/International_Securities_Identification_Number) ANNA's FAQ says that, as a general rule, ISINs should never be re-used.[[3]](https://anna-web.org/faq-page/) ANNA describes ISO 6166 as recognised by many regulators as the primary identifier required for transaction reporting.[[3]](https://anna-web.org/faq-page/) Wikipedia notes that European regulations such as the Solvency II Directive 2009 increasingly require the ISIN to be reported.[[1]](https://en.wikipedia.org/wiki/International_Securities_Identification_Number) The python-stdnum library's isin module checks the length and check digit of an ISIN.[[2]](https://arthurdejong.org/python-stdnum/doc/2.2/stdnum.isin) The python-stdnum documentation notes that the module does not separately validate the embedded national security identifier, such as a CUSIP.[[2]](https://arthurdejong.org/python-stdnum/doc/2.2/stdnum.isin) Store ISINs as text, upper-case them and check the digit, but remember that a passing check digit only shows the code is well formed, not that any agency issued it. (Meridian's view) ANNA offers a free ISIN Lookup Service where ISINs with basic information can be looked up.[[3]](https://anna-web.org/faq-page/) ### Where you'll meet it GLEIF publishes daily ISIN-to-LEI relationship files, linking newly issued ISINs to Legal Entity Identifiers, which are publicly available on its website.[[4]](https://www.gleif.org/en/lei-data/lei-mapping/download-isin-to-lei-relationship-files) GLEIF and ANNA piloted the first daily ISIN-to-LEI relationship files in April 2019.[[4]](https://www.gleif.org/en/lei-data/lei-mapping/download-isin-to-lei-relationship-files) ## Sources 1. [International Securities Identification Number - Wikipedia](https://en.wikipedia.org/wiki/International_Securities_Identification_Number) — secondary source 2. [stdnum.isin — python-stdnum 2.2 documentation](https://arthurdejong.org/python-stdnum/doc/2.2/stdnum.isin) — documentation 3. [ANNA FAQs - Your Common Questions Answered](https://anna-web.org/faq-page/) — organisation 4. [Download ISIN-to-LEI Relationship Files - LEI Mapping - LEI Data – GLEIF](https://www.gleif.org/en/lei-data/lei-mapping/download-isin-to-lei-relationship-files) — dataset 5. [CNMV - ANNA: Association of National Numbering Agencies.](https://internet.cnmv.es/portal/ancv/anna?lang=en) — organisation 6. [About CGS Identifiers - CUSIP Global Services](https://www.cusip.com/identifiers.html) — documentation