LEI
A global 20-character code that identifies a legal entity in financial transactions, defined by ISO 17442.
When Lehman Brothers went down in 2008, regulators spent weeks working out who was exposed to whom, because the same company went by different names in every system. The G20 asked for a common identifier, and GLEIF was set up in Basel in 2014 to run it. The code is 20 characters long, the last two being check digits computed with the same mod 97 algorithm IBAN uses.
LEIs went mainstream with MiFID II in January 2018: no code, no trading in securities, and brokers spent the preceding weeks phoning surprised clients. The code has to be renewed every year for a fee, which is why a large share of the register shows as lapsed. ISO 20022 messages have a dedicated field for it, and GLEIF's open database also records who owns whom.