[citation needed] ISINs slowly gained traction worldwide and became the most popular global securities identifier.
Trading, clearing and settlement systems in many countries adopted ISINs as a secondary measure of identifying securities.
Some countries, mainly in Europe, moved to using the ISIN as their primary means of identifying securities.
[3] ISO 6166 (or ISO6166:2021 as of the 2021 revision[4]) defines the structure of an International Securities Identification Number (ISIN).
[citation needed] Each country has a national numbering agency responsible for issuing ISINs.
[5] Since existing national numbering schemes administered by the various NNAs form the basis for ISINs, the methodology for assignment is not consistent across agencies globally.
[citation needed] The ISIN is included in services sold by financial data vendors and intermediaries.
The issuer of a security will include the ISIN in issuance papers or other documentation for identification purposes.
In 2009, Standard & Poor's was charged by the European Commission (EC) with abusing its position in licensing international securities identification codes for United States securities by requiring European financial firms and data vendors to pay licensing fees for their use.
"This behaviour amounts to unfair pricing," the EC said in its statement of objections which lays the groundwork for an adverse finding against S&P.
Some protocols require the transmission of additional check digits added to the full ISIN number.