How to read a CUSIP
Unless you're in a certain line of business, it's unlikely you'll ever need to know the CUSIP code for one of your investments. But here's how the nine-digit numbers are broken down, using the 037833100 CUSIP of Apple (AAPL -3.40%) as an example:
- The first six characters, known as the CUSIP-6, are the base, identifying the issue. In this case, Apple’s base is 037833.
- The next two numbers identify the type of security; numbers are usually used for stocks, and letters are saved for fixed-income securities. The first security issued is assigned a number 10; subsequent issues add another 10, until the last number becomes 80. The next issue is 88, then decreases by 10.
- The final digit is an automated check digit that verifies the accuracy of the previous numbers; some clearinghouses ignore the ninth digit or just drop it.
Likewise, CUSIP 594918104 identifies Microsoft (MSFT -2.17%).
CUSIPs also don't have to remain constant. For example, CUSIP 38259P508 had been Google’s identifier. When the company changed its name to Alphabet (NASDAQ:GOOG, NASDAQ:GOOGL) in 2015, its CUSIP became 02079K305. As with other CUSIPs, the first six characters identify the security as originating from Alphabet; the next two, "30," indicate it's the third issue. The last digit is called a "checksum" that verifies the accuracy of the previous characters.