ISIN vs CUSIP: Differences, Costs, and How to Find Them

An ISIN and a CUSIP identify the same security at different scales: the CUSIP is a nine-character code used across the United States and Canada, and the ISIN is a 12-character code used internationally that carries the CUSIP inside it for U.S.-registered securities. In the ISIN vs CUSIP comparison, the two are not competing systems but nested ones. Domestic trading, clearing, and SEC reporting run on the CUSIP. Cross-border trades and non-U.S. regulators run on the ISIN.

What a CUSIP Is

CUSIP stands for Committee on Uniform Security Identification Procedures. It is the standard identifier for stocks, bonds, and other financial instruments issued in the United States and Canada, managed by CUSIP Global Services (CGS) on behalf of the American Bankers Association.¹ A security needs a CUSIP before it can trade on any regulated North American exchange, which is why issuers apply for one early in the offering process.²

The nine characters break into three parts. The first six identify the issuer: a specific company, municipality, or government entity. The next two identify the specific instrument from that issuer, distinguishing, for example, common stock from a preferred class or one bond maturity from another. The ninth character is a check digit calculated with the Luhn algorithm (also called modulus 10), which catches transcription errors before they cause a failed settlement.¹

Every party to a trade, from brokers to custodians to clearinghouses, references the same CUSIP to confirm they are talking about the exact same instrument. That shared reference is what keeps clearing from breaking down.

What an ISIN Is

ISIN stands for International Securities Identification Number. It is a 12-character alphanumeric code defined by ISO 6166 and designed to work in every jurisdiction worldwide.³ Where the CUSIP handles identification within North America, the ISIN wraps whatever local identifier a country already uses inside a universal format.

The 12 characters break into three parts. The first two are a country code following ISO 3166-1, indicating where the security is registered; U.S. securities start with “US,” German securities with “DE.” The next nine are the National Securities Identifying Number assigned by that country’s own numbering agency. The final character is a check digit calculated with a modulus 10 “Double-Add-Double” formula that verifies the preceding eleven.

National Numbering Agencies (NNAs) issue ISINs under the coordination of the Association of National Numbering Agencies (ANNA). In countries without their own NNA, neighboring agencies administer the codes.⁴

How the CUSIP Fits Inside a U.S. ISIN

For any U.S.-registered security, the CUSIP is not a separate code from the ISIN. It is literally the middle nine characters of it. Building a U.S. ISIN from a CUSIP is mechanical: prefix “US” and append the ISIN check digit.⁴ Apple Inc.’s CUSIP is 037833100; its ISIN is US0378331005.

The same nesting applies elsewhere with different local codes. A German ISIN begins with “DE” and carries the six-digit Wertpapierkennnummer (WKN) inside it.⁵ A UK ISIN begins with “GB” and carries a seven-character SEDOL code assigned by the London Stock Exchange. In every case the ISIN wraps the local identifier without replacing it.

CGS also maintains the CUSIP International Numbering System (CINS), a nine-character code in the same format as a CUSIP but with a letter in the first position to indicate the issuer’s country or region. A CUSIP or CINS identifier always occupies positions three through eleven of a CGS-issued ISIN.¹

When You Need a CUSIP and When You Need an ISIN

The practical rule: use the CUSIP inside U.S. markets and the ISIN when anything about the transaction crosses a border.

Domestic U.S. Operations Run on CUSIP

Trade execution, order management, clearance, and settlement inside the United States use the CUSIP. The Depository Trust and Clearing Corporation (DTCC) and its subsidiaries process trades against it. Institutional investment managers with $100 million or more in qualifying securities file quarterly Form 13F reports with the SEC, and Column 3 of that form requires the nine-digit CUSIP for every holding.⁶ The municipal bond market is equally CUSIP-dependent: the MSRB’s EMMA system uses the CUSIP as the primary lookup key for investors researching a specific bond.²

Cross-Border Reporting Runs on ISIN

Once a transaction crosses a border, the ISIN takes over. Exchanges and regulators outside North America require the ISIN for transaction reporting and trade confirmation. The European Union’s Markets in Financial Instruments Regulation (MiFIR) requires the ISIN for detailed reporting of financial instrument transactions, and this mandate covers every investment firm subject to EU regulation. A U.S. institution trading a domestic corporate bond uses the CUSIP internally, but must supply the full ISIN when reporting that same transaction to a European regulator.

Firms with cross-border business maintain mapping tables between every CUSIP and its corresponding ISIN. An investor buying shares of a U.S. company through the London Stock Exchange uses the ISIN for confirmation, clearing, and ownership registration, even though the original CUSIP sits inside that ISIN and remains recognized by the U.S. side.

What Each Identifier Costs

Individual investors do not pay for identifiers. Issuers do. For a standard offering requiring a single CUSIP, CGS charges an assignment fee of $210. Offerings with multiple maturities or classes cost $210 for the first identifier and $34 for each additional one. Short-term municipal notes and certificates of deposit under one year have a reduced fee of $105 each.⁷

ISIN fees depend on the National Numbering Agency. For conventional securities such as stocks and bonds, the ISIN assignment fee varies by country and is typically bundled with other listing or registration costs charged by the local NNA. Bulk access to CUSIP data itself also carries a separate licensing fee from CGS, though firms maintaining fewer than 500 securities containing CUSIP data in their internal database qualify for a fee waiver, and anyone viewing CUSIP numbers through an authorized vendor’s screen pays nothing.⁸

How to Find the CUSIP or ISIN for a Security You Own

The fastest place to find either identifier is your brokerage account. Statements and trade confirmations typically print the CUSIP alongside the security’s name and description. A bond’s offering document or prospectus lists it prominently. For municipal bonds specifically, the MSRB’s EMMA website lets you search by CUSIP for free.²

If you already have the CUSIP for a U.S. security and need the ISIN, the construction is mechanical: add “US” to the front and calculate the check digit at the end. Most financial data platforms display both identifiers on a security’s detail page, so building the ISIN by hand is rarely necessary. For non-U.S. securities, the ISIN is usually the primary identifier displayed on international brokerage platforms and exchange sites.

Other Identifiers You May Encounter

CUSIP and ISIN are the two you will meet most often, but they are not the only codes in circulation, and knowing what the others do keeps you from confusing them for the same thing.

SEDOL: the Stock Exchange Daily Official List, a seven-character code assigned by the London Stock Exchange. It is the local identifier for UK and Irish securities and forms the middle section of those countries’ ISINs.
WKN: the Wertpapierkennnummer, a six-digit alphanumeric code that was Germany’s primary security identifier before ISIN adoption in 2003 and is still used domestically.⁵
FIGI: the Financial Instrument Global Identifier, a 12-character code designed as an open, freely available alternative to proprietary identifiers. The SEC now allows optional FIGI reporting alongside CUSIP on Form 13F.⁶
LEI: the Legal Entity Identifier, a 20-character code that identifies the entity behind a transaction rather than the security itself. The EU enforces a “no LEI, no trade” policy under MiFID II, requiring counterparties to hold an LEI before executing reportable transactions.⁹

The LEI identifies who is trading; the CUSIP and ISIN identify what is being traded. Issuers can now request a CUSIP and an LEI through a single application process with CGS.⁹

1
CUSIP Global Services. Identifiers
2
Municipal Securities Rulemaking Board. About CUSIP Numbers
3
Association of National Numbering Agencies (ANNA). ISIN Uniform Guidelines Relating to ISO 6166 – Version 22, December 2023
4
ISIN Organization: international securities identification numbers organization. About International Securities Identification Number (ISIN)
5
Deutsche Börse Group. WKN
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SEC.gov. Form 13F Information Required of Institutional Investment Managers
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CUSIP Global Services. Fees for CUSIP Assignment
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CUSIP Global Services. CGS License Fees For End-User Customers CGS Licensing Policies FAQs
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S&P Global Market Intelligence. CUSIP and LEI – Two Standards, One Stop – Transcript