> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.withpersona.com/2020-05-18/reference-ids/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.withpersona.com/_mcp/server.

# Reference IDs

> Use reference IDs to identify users and link multiple Inquiries to one Account.

A reference ID is a string that you assign to identify a unique end user in Persona.

A reference ID lets you link multiple Persona inquiries to a single Persona [account](/accounts). Inquiries created with the same reference ID are automatically associated with the same account.

> **Info**
>
> #### Best practice
>
> Persona recommends you provide a reference ID for an inquiry whenever possible.

### Using reference IDs

You should assign the same reference ID to every inquiry you create for a single end user. This helps you:

* Easily look up the status of all interactions between this user and Persona
* More easily re-verify the user
* Guard against a user [creating multiple inquiries](/prevent-users-from-creating-multiple-inquiries)

### Choosing a reference ID

The value you choose as the reference ID can help you tie a Persona account back to your business.

Persona recommends you use the "user ID" of a user within your internal systems as the corresponding reference ID for their Persona inquiries. This provides a clear way to tie each Persona account back to your systems.

> **Warning**
>
> #### Reference IDs and PII
>
> Prefer using UIDs instead of sensitive information such as email addresses. Persona does not treat reference IDs as PII.

### Setting a reference ID

Your Persona integration method determines how you set a reference ID:

* [**Server API**](/api-reference/inquiries/create-an-inquiry) (recommended): Pass the reference ID in the `auto-create-account-reference-id` field in the `meta` object in your request payload
* [**Embedded**](/embedded-flow-parameters): Pass the field to the `referenceId` parameter in the embed code
* [**Hosted**](/hosted-flow-parameters): Include the reference ID as a query string parameter (`&reference-id=abc`)

You can also set a reference ID on an existing Persona account [through the API](/api-reference/accounts/update-an-account).

> Use reference IDs to identify users and link multiple Inquiries to one Account.