I found that for example ISIN have following rules:

Merger and acquisition: Old ISINs for stock become inactive and are replaced by securities with a new ISIN. Bonds only need new ISINs if old ones are exchanged for new ones.

So ISIN could be changed for a company.

I suppose the same rules are for CUSIP/SEDOL (an i right?)

Is there any way to link the new ISIN (CUSIP/SEDOL) with the old one? I mean when some companies were merged, and i have a ISIN of the new company - how can i see which companies the new company consists of (get ISINS(CUSIP/SEDOL) of initial companies)?

The same is for all ISIN (CUSIP/SEDOL) histories? Is it possible to get all ISINs for a company (for all periods)?

  • $\begingroup$ P.S. Could someone tell in which cases CUIP is changed? Is it Name change or it could be changed manually without a reason? $\endgroup$
    – kban
    Commented Dec 10, 2019 at 7:33

2 Answers 2


CUSIPs, ISINs, SEDOLs, etc are identifiers for securities (stocks, bonds, and sometimes other instruments), not for companies. For example, one company might have several classes of common stock; each has its own cusip. Companies have other identifiers. As Kurtosis wrote, there's an industry trend to use LEIs as company id's.

Empirically, the various organizations that assign identifiers to securities usually don't change bond identifiers, but do change stock identifiers when a company/issuer merely changes name or reorganizes.

I'm not aware of any written rules, but most corporate actions seem to result in a "new" stock with new identifiers. (But be careful, occasionally a merger or a spin-off totally changes the nature of the company, yet the stock identifiers don't change.)

Typical scenarios where bond identifier changes might be: a company issues 144A and Reg S tranches of a bond, each with its own ISIN. Some time later the company issues a Global tranche, with a new ISIN, and the old tranches are converted to the new one and cease to exist. A company issues a bond, goes through bankruptcy, issues a totally new bond with longer maturity given to old bondholders in exchange for the old one.

But most corporate actions don't change a bond id, even through the bond might have a totally different issuer/guarantor than when it weas issued.

CRSP database has a good history of corporate actions going back decades, but is very U.S.-centric.


Your best bet at linking a company across ISIN or CUSIP changes is to go with their legal entity ID (LEI). That said, sometimes you need to actually read through the news to determine if the company is the same or if the company name and legal structure was changed slightly or more.

Note also that CUSIPs do not generally change without reason, but CUSIPs do get reused. A CUSIP is only uniquely identifying within a specified time period.


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