A CUSIP number is a 9-character alphanumeric identifier assigned to US and Canadian financial securities. Used for stocks, bonds, mutual funds, and other instruments, the last character is a check digit computed using a Luhn-variant algorithm. Enter any CUSIP below to verify its check digit and parse the issuer code and issue number.
Validation Checks
CUSIP Breakdown
How to Use This CUSIP Number Validator
CUSIP numbers are the backbone of US securities identification, appearing on every stock certificate, bond prospectus, mutual fund statement, and trade confirmation in American financial markets. This CUSIP number validator checks the check digit using the official Luhn-variant algorithm and breaks down the issuer code and issue number components.
Step 1: Enter the CUSIP
Type or paste the 9-character CUSIP into the input field. The validator accepts alphanumeric characters (A-Z and 0-9) and converts lowercase to uppercase automatically. CUSIPs are always exactly 9 characters — no spaces, hyphens, or other punctuation. You can also click one of the example buttons to load a well-known security like Apple (037833100) or a US Treasury bill.
Step 2: Understand the Three Parts
Every CUSIP has three segments. The first 6 characters are the issuer code — a unique code assigned to each company or government entity by the CUSIP Service Bureau. The next 2 characters (positions 7-8) are the issue number, which distinguishes between different securities from the same issuer (e.g., Class A vs Class B shares, or different bond series). The 9th character is the check digit, which is mathematically derived from the first 8 characters.
How the Check Digit Works
The CUSIP check digit algorithm assigns numeric values to each character: digits keep their face value; letters A=10, B=11 through Z=35; asterisk=36, @=37, #=38. Even-positioned characters (positions 2, 4, 6, 8) are doubled. All digit sums from the resulting values are added together. The check digit is (10 - (sum % 10)) % 10. This catches single-character substitutions and most transposition errors.
Common Issuer Code Patterns
Certain issuer code prefixes identify security types. US government securities use issuer codes starting with 912 (e.g., 912828 for standard Treasury notes). Municipal bonds use state-specific codes. American Depositary Receipts (ADRs) typically have issuer codes ending in specific alphanumeric patterns. Corporate equities use codes assigned to the issuing company — Apple's code is 037833, Microsoft's is 594918, and Amazon's is 023135. Recognizing these patterns helps verify that a CUSIP belongs to the expected type of security.
FAQ
What is a CUSIP number?
CUSIP (Committee on Uniform Security Identification Procedures) is a 9-character alphanumeric identifier used to uniquely identify financial securities in the United States and Canada. Developed by the American Bankers Association in 1968 and now administered by FactSet, CUSIPs are assigned to stocks, bonds, mutual funds, and other securities. They appear on brokerage statements, trade confirmations, and corporate filings with the SEC. The last character is always a check digit that mathematically validates the other 8 characters.
How does CUSIP check digit validation work?
The CUSIP check digit uses a Luhn-variant algorithm designed for alphanumeric strings. Each of the first 8 characters is converted to a number: digits keep their face value, A=10, B=11 through Z=35, while * (asterisk)=36, @=37, #=38. Even-positioned characters (positions 2, 4, 6, 8, using 1-based indexing) are multiplied by 2. All resulting digit sums are added together. The check digit equals (10 minus (sum modulo 10)) modulo 10. This single digit catches single-character substitution errors and most transpositions.
What is the difference between a CUSIP and an ISIN?
A CUSIP identifies securities in the US and Canada, while an ISIN (International Securities Identification Number) is a global 12-character identifier used worldwide. For US securities, the ISIN is simply 'US' + CUSIP + a single check digit computed on the combined string. Most US securities have both a CUSIP and an ISIN. CUSIPs are used for domestic US trading and settlement; ISINs are used for international reporting and cross-border transactions under MiFID II and other regulations.
Can I look up a company's CUSIP number?
CUSIP numbers are assigned by FactSet and can be looked up through SEC EDGAR filings (all US public companies disclose their CUSIP in prospectuses and 10-K filings), Bloomberg terminals, or through your broker's securities database. This tool validates the format and check digit of a known CUSIP but does not look up company or security information. For live CUSIP lookups, visit SEC EDGAR at sec.gov/cgi-bin/browse-edgar or your brokerage platform.
Is my data safe when using this tool?
Yes. The CUSIP validator runs entirely in your browser using client-side JavaScript. No data is sent to any server or stored anywhere. All check digit calculations happen locally on your device. You can disconnect from the internet and the tool will continue to work.
What does a CUSIP issuer code tell me?
The first 6 characters of a CUSIP are the issuer code. For corporate securities, this is a 6-character code assigned to the company. For US government securities, the issuer code starts with '9' (e.g., '912828' for US Treasuries). For municipal bonds, it starts with a digit representing the state. The next 2 characters (positions 7-8) are the issue number that distinguishes between a company's different securities — different share classes, bond series, or other instruments from the same issuer.