---
title: "What is a LUSID Instrument ID, or LUID?"
slug: "what-is-a-lusid-instrument-id-or-luid"
updated: 2025-06-23T07:34:44Z
published: 2025-06-23T07:34:44Z
canonical: "support.lusid.com/what-is-a-lusid-instrument-id-or-luid"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://support.lusid.com/llms.txt
> Use this file to discover all available pages before exploring further.

# What is a LUSID Instrument ID, or LUID?

When you [create an instrument](/v1/docs/how-do-i-master-an-instrument), LUSID automatically generates a LUSID Instrument ID (also known as a LUID), for example `LUID_3L7Z8RWD`.

A LUID is an internal identifier that is guaranteed to be unique to your domain and never change. You cannot edit or delete an instrument's LUID. If you have chosen to partition your instrument master into [scopes](/v1/docs/understanding-instrument-scopes), an instrument's LUID is unique across all scopes, even if the 'same' instrument exists in multiple scopes.

A LUID has:

- An identifier type of `LusidInstrumentId`.
- A 3-stage key of `Instrument/default/LusidInstrumentId` (you may need to address the instrument using this key).
- A value that starts with `LUID_` for a non-currency instrument.
- A value that starts with `CCY_` for a currency instrument.

The following LUIDs are reserved:

- `LUID_ZZZZZZZZ` for the [unknown instrument](/v1/docs/what-is-the-unknown-instrument-or-luid-zzzzzzzz)
- `CCY_ZZZ` for the [unknown currency](/v1/docs/what-is-the-unknown-instrument-or-luid-zzzzzzzz#a-note-on-the-unknown-currency)
- `CCC_XXX` for a 'transaction' involving [no currency](https://en.wikipedia.org/wiki/ISO_4217#X_currencies).