> For the complete documentation index, see [llms.txt](https://help.security.gallagher.com/knowledge-hub/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.security.gallagher.com/knowledge-hub/accessnow-user-guide/system-administration/command-centre-integration/set-command-centre-unique-identifiers.md).

# Set Command Centre unique identifiers

In Gallagher Command Centre, a **Unique Personal Data Field (Unique PDF)** is a custom text or numeric field configured with the "Unique Values" constraint. It serves as the primary key for identifying individual cardholders across integrated software systems, including AccessNow.

{% hint style="info" %}
AccessNow usually uses an **email** **address** or **employee ID** PDF as the cardholder's unique identifier.
{% endhint %}

#### Key Characteristics of a Unique PDF

* **Duplicate prevention:** Prevents operators or automated interfaces from entering the same identifier across multiple cardholders. Blank or null values are allowed across multiple records.
* **System restrictions:** To protect database integrity, Unique PDFs cannot have a default value. They are excluded from Cardholder Bulk Changes to prevent accidental mass overwrites.
* **Syntax validation:** You can configure regular expressions to enforce specific formats. For example, an Employee ID can require two uppercase letters followed by six numbers.

## How to set a Unique PDF in Command Centre

{% stepper %}
{% step %}

### Open Personal Data Fields in Command Centre Configuration Client

Alternatively, click **Personal Data Field** on the **Administration** toolbar in Command Centre Client.
{% endstep %}

{% step %}

### Choose the Email PDF or Employee ID

Choose the PDF you want to set as unique. For AccessNow, this is usually the email address or employee ID. Make sure the PDF is assigned to an Access Group so cardholders inherit the field.
{% endstep %}

{% step %}

### Check the Unique Values checkbox

Select the **Unique Values** checkbox. Optionally, use the **Regular Expression** setting and enter syntax in the **Syntax** box to enforce formatting.
{% endstep %}

{% step %}

### Save the PDF

{% endstep %}
{% endstepper %}


---

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