ISIN vs CUSIP: Differences, Uses, and Issuer Costs

ISIN vs CUSIP comes down to reach: a CUSIP is the nine-character code that identifies stocks, bonds, and other securities issued in the United States and Canada, while an ISIN is the 12-character code used to identify securities globally. Every U.S.-registered security has both, because the CUSIP sits inside the ISIN as its core. Which one you need depends on where the trade or report is going.

What Each Code Looks Like

The CUSIP is nine characters, assigned by CUSIP Global Services (CGS) on behalf of the American Bankers Association.¹ It splits into three parts:

Characters 1–6 identify the issuer (a company, municipality, or government entity).
Characters 7–8 identify the specific instrument from that issuer, such as common stock versus a preferred class or a specific bond maturity.
Character 9 is a check digit calculated with the Luhn (modulus 10) algorithm to catch transcription errors before a trade fails to settle.

Brokers, custodians, and clearinghouses all reference the same CUSIP to confirm they are talking about the same instrument, which is what lets clearing and settlement run cleanly.¹

The ISIN is 12 characters, defined by ISO 6166 and designed to work across every jurisdiction.² Its structure:

Characters 1–2 are the country code from ISO 3166-1. U.S. securities begin with “US,” German securities with “DE,” UK securities with “GB.”
Characters 3–11 are the National Securities Identifying Number, which is whatever local code that country’s numbering agency uses. In the United States, that local code is the CUSIP.
Character 12 is a check digit calculated with a modulus 10 “Double-Add-Double” formula that verifies the preceding 11 characters.

National Numbering Agencies in each country issue ISINs, coordinated globally by the Association of National Numbering Agencies (ANNA). Where a country has no agency of its own, a neighboring one steps in.³

How the Two Fit Together

For a U.S. security, the ISIN is built directly from the CUSIP. Add “US” to the front, add the ISIN check digit to the end, and that is the ISIN.³ Apple’s common stock CUSIP is 037833100; its ISIN is US0378331005.

The same embedding pattern applies elsewhere with a different local code in the middle. A German ISIN starts with “DE” and carries the six-digit Wertpapierkennnummer (WKN), Germany’s legacy identifier.⁴ A UK ISIN starts with “GB” and carries the seven-character SEDOL code assigned by the London Stock Exchange. The ISIN wraps the local identifier in a globally recognizable format without replacing it.

When You Need a CUSIP and When You Need an ISIN

Inside the United States, the CUSIP is the working identifier. The Depository Trust and Clearing Corporation and its subsidiaries use CUSIPs to process trades, and domestic trade execution, order management, clearance, and settlement all run on them. Institutional investment managers with $100 million or more in qualifying securities file quarterly Form 13F reports with the SEC, and Column 3 of the reporting table requires the nine-digit CUSIP for each holding.⁵ The municipal bond market runs on CUSIPs too: the MSRB’s EMMA system uses them as the primary lookup key for investors researching individual bonds. A security has to have a CUSIP before it can trade on any regulated North American exchange, so issuers apply for one early in the offering process.⁶

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 by every investment firm subject to EU regulation. A U.S. institution trading a domestic corporate bond will use the CUSIP internally, then provide the full ISIN when reporting that same transaction to a European regulator. An investor buying a U.S.-issued share through the London Stock Exchange sees the ISIN on trade confirmations, clearing records, and registration, even though the original CUSIP is still embedded inside it.

One narrow variant is worth flagging so you don’t mistake it for something else: for privately placed debt, CGS issues a Private Placement Number (PPN) in the same nine-character format but with special characters like *, @, or # in positions six through eight. The National Association of Insurance Commissioners requires insurers to use PPNs when reporting private investments.⁷

How to Look Up an Identifier for a Security You Own

Most individual investors never request a new CUSIP or ISIN; they just need to find the one that already exists. Brokerage account statements and trade confirmations usually print the CUSIP next to the security description. Bond offering documents and prospectuses list it prominently. For municipal bonds, the MSRB’s EMMA website lets you search by CUSIP for free.⁶

Once you have the CUSIP for a U.S. security, the ISIN is mechanical: “US” in front, check digit at the back. Most financial data platforms display both on the same security detail page, so you rarely have to construct one by hand. For non-U.S. securities, the ISIN is usually the primary identifier shown on international brokerage platforms and exchange websites.

Bulk access to the CUSIP database is not free. CGS licenses the data, with fees that scale by how many identifiers a firm uses, how many business lines access it, and how many regions the firm operates in. Firms with fewer than 500 securities containing CUSIP data in their internal database qualify for a fee waiver, and simply viewing CUSIP numbers through an authorized vendor’s screen display costs nothing.⁸

What It Costs an Issuer to Get One

If you are on the issuing side rather than the investing side, the fees are set by the assigning agency. For a standard offering requiring a single CUSIP, CGS charges $210. Offerings with multiple maturities or classes are $210 for the first identifier and $34 for each additional one. Short-term municipal notes and certificates of deposit under one year cost $105 each.⁹

ISIN fees vary by country because they are set by each National Numbering Agency, and for conventional securities the ISIN cost is typically bundled with other listing or registration costs through the local NNA. Over-the-counter derivatives are handled separately by the ANNA Derivatives Service Bureau, which charges institutional users by tier: standard users pay €28,946 per invoicing period for up to 100 new ISINs, and power users pay €86,839 for up to 5,000.¹⁰

Related Codes You May See

A few other identifiers show up alongside CUSIP and ISIN and are worth recognizing:

SEDOL is a seven-character code from the London Stock Exchange, used as the local identifier for UK and Irish securities and embedded inside their ISINs.
WKN is Germany’s six-digit alphanumeric identifier, in use since before Germany adopted the ISIN in 2003, and still embedded in German ISINs today.⁴
FIGI, the Financial Instrument Global Identifier, is a 12-character open identifier meant as a freely available alternative to proprietary codes. The SEC allows optional FIGI reporting alongside CUSIP on Form 13F.⁵
LEI, the Legal Entity Identifier, is a 20-character code that identifies the entity behind a transaction rather than the security itself. It was created after the 2008 financial crisis so regulators could trace firm-level exposures across the global system, and the EU enforces a “no LEI, no trade” policy under MiFID II.¹¹

None of these replaces the CUSIP-and-ISIN pair for identifying a security. They sit alongside it, each solving a different problem: SEDOL and WKN as local identifiers, FIGI as an open cross-market reference, LEI as an entity-level identifier that pairs with the ISIN in regulatory reporting.

1
CUSIP Global Services. Identifiers
2
Association of National Numbering Agencies (ANNA). ISIN Uniform Guidelines Relating to ISO 6166 – Version 22, December 2023
3
ISIN Organization: international securities identification numbers organization. About International Securities Identification Number (ISIN)
4
Deutsche Börse Group. WKN
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SEC.gov. Form 13F Information Required of Institutional Investment Managers
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Municipal Securities Rulemaking Board. About CUSIP Numbers
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CUSIP Global Services. CGS Private Placement Numbers
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CUSIP Global Services. CGS License Fees For End-User Customers CGS Licensing Policies FAQs
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CUSIP Global Services. Fees for CUSIP Assignment
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DSB – Derivatives Service Bureau. OTC ISIN Fee Breakdown for 2026
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S&P Global Market Intelligence. CUSIP and LEI – Two Standards, One Stop – Transcript