instrument-identifiers

July 11, 2026 · View on GitHub

Securities identifier math in one package — CUSIP, ISIN, SEDOL, FIGI, and LEI: validation, parsing, check-digit computation, and CUSIP→ISIN / SEDOL→ISIN conversion. Zero dependencies.

npm install instrument-identifiers

Why

Every trading, settlement, or reference-data system juggles at least three identifier schemes, and each has its own check-digit algorithm (CUSIP's mod-10 double-add-double, ISIN's ISO 6166 Luhn, SEDOL's 1-3-1-7-3-9 weights, FIGI's OMG spec, LEI's ISO 7064 MOD 97-10). npm had them scattered across single-purpose validators — several dead, none doing conversion. This package is the whole set, strictly the free algorithm layer: no licensed identifier database content.

import { isValidCusip, cusipToIsin, parseIsin, identify } from "instrument-identifiers";

isValidCusip("91282CQQ7");     // true — a live Treasury note
cusipToIsin("037833100");      // "US0378331005" — Apple, real ISIN reproduced
parseIsin("US0378331005");     // { countryCode: "US", nsin: "037833100", checkDigit: 5 }
identify("BBG000B9XRY4");      // ["FIGI"]

API

Per identifier — isValidX(value), xCheckDigit(base), and where the structure is meaningful, parseX(value):

Identifier	Validate	Check digit	Parse	Convert
CUSIP (9)	`isValidCusip`	`cusipCheckDigit(base8)`	`parseCusip` → issuer/issue	`cusipToIsin(cusip, cc?)`
ISIN (12)	`isValidIsin`	`isinCheckDigit(payload11)`	`parseIsin` → country/NSIN	—
SEDOL (7)	`isValidSedol`	`sedolCheckDigit(base6)`	—	`sedolToIsin(sedol, cc?)`
FIGI (12)	`isValidFigi`	`figiCheckDigit(base11)`	`parseFigi` → prefix/id	—
LEI (20)	`isValidLei`	`leiCheckDigits(base18)`	—	—

Plus identify(value) → every type the value validly matches. Inputs are case-insensitive; validators return booleans, everything else throws RangeError on malformed input. Format rules are enforced (FIGI's mandatory G, excluded country-like prefixes, SEDOL's no-vowels alphabet).

Correctness

Real-world anchors: Apple's CUSIP/ISIN/FIGI/LEI, a live US Treasury CUSIP, BAE's SEDOL→ISIN — each reproduced, not just validated.
Cross-checked against an independent Python reference implementation (test/generate-fixtures.py): 300+ generated identifiers per run, every one validated and its check digit recomputed, plus corruption tests (every fixture with a damaged check digit must fail).

Part of a small fixed-income toolkit: 32nds · day-count · accrued-interest · sifma-holidays · treasurydirect · tbill · newyorkfed.

Author

Built by Moshe Malka — engineering leader in New York City. Studio work at Quentin.Code.

Why

API

Correctness

Related

Author