CUSIP Identification, Change Tracking, and Stable Security Links
Summary
The document explains that CUSIPs are assigned identifiers for specific securities and are generally immutable once assigned, rather than values that simply change in place. It describes the identifier as having a base associated with the issuer and a tail identifying the security. A proprietary CUSIP Global Services master file is presented as a consolidated source of newly assigned identifiers, with updates available at different frequencies; access requires a subscription. A lookup form is mentioned as a limited way to check an old identifier, while CRSP is suggested for tracking changes.
The answers also caution that apparent changes can arise from different corporate events, including name changes, mergers, spin-offs, and reorganizations. Researchers linking historical market data should therefore distinguish a new identifier from continuity of the underlying security. The document recommends using persistent research identifiers such as CRSP permanent numbers or Compustat company identifiers when appropriate. It does not establish that every event can be mapped automatically, and identifier relationships may require event-specific verification.
Key ideas
- A CUSIP is assigned to a particular security and is generally treated as immutable.
- The CUSIP master file offers consolidated assignment information but requires paid access.
- Corporate events can create new identifiers, and the relationship to an earlier security depends on the event.
- Stable research identifiers can be preferable to CUSIPs when linking historical company or security data.
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Full text
# How to get know when CUSIP is changed # How to get know when CUSIP is changed CUSIP code is not a constant, it could be changed. Does anybody know how to detect a CUSIP change? Is there any report with this info? Where can i find it? Thank you. ## Answer by Thomas Boyd (score 3) https://quant.stackexchange.com/a/53993 The framework that manages CUSIP assignment is proprietary and managed by CUSIP Global Services (a subsidiary of S&P Global). The CUSIP Global Services Master File is web-based platform & API system that provides a wide-range of CUSIP data points, including newly assigned identifiers at daily, weekly and even intraday increments. Without subscribing to the CSG Master File , there isn't an actively maintained, consolidated repository of CUSIP information available. It should be noted however that CUSIP assignments do not simply "change". Think of a CUSIP like a barcode. Each CUSIP contains alpha-numerically enumerated information about a securities issuing entity (usually the first 6 digits, the "base"), and the specific security (7th and 8th digit, the "tail"). Once an equity issue, debt security etc. has been assigned a barcode, that barcode is unique and immutable. CUSIP Structure: https://www.cusip.com/identifiers.html#/CUSIP Accessing the CUSIP Master File: https://www.cusip.com/pdf/CGS079_CGS_CUSIP_Master_File_02_15_17_US_Ltr.pdf ## Answer by dkhokhlov (score 0) https://quant.stackexchange.com/a/50221 Use this form to search by old CUSIP: https://quotes.fidelity.com/mmnet/SymLookup.phtml the form will return - not found - if CUSIP changed. ## Answer by Dimitri Vulis (score 0) https://quant.stackexchange.com/a/53991 A stock cusip changes whenever the company name changes (unlike, e.g. bond cusips). In this case, you can assume that the old cusip and the new cusip refer to the same stock, and all the historical data is still applicable. But there may be other reasons for a cusip change, such as corporate mergers or spin-offs or re-organizations. You'd be better off using CRSP id (permo) or CompuStat gvkey as your primary identifier rather than a cusip. If you must track cusip changes, I suggest you get this information from CRSP.
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