> For the complete documentation index, see [llms.txt](https://docs.nexusglobalpayments.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.nexusglobalpayments.org/addressing-and-proxy-resolution/role-of-the-proxy-directory-operator-pdo.md).

# Role of the Proxy Directory Operator (PDO)

In most IPS, a proxy (or "alias") cannot be used directly in a payment instruction (such as ISO 20022 [`pacs.008`](https://github.com/bis-ih-fusse/nexus-temp/blob/main/messaging-and-translation/message-pacs.008-fi-to-fi-customer-credit-transfer)). Instead, the proxy must first be sent to the local **proxy directory**, via a proxy resolution request. The proxy directory service will then lookup and return the corresponding account details.

**Proxy Directory Operators (PDOs)** provide and maintain the databases which contain a list of proxies and the accounts and FIs that each proxy is associated with.

PDOs typically provide:

* A **database of proxies** and associated Financial Institution Identifications and Account Identifications
* A method for account holders to **register and deregister proxies**, or change the account linked to a specific proxy, via their authorized PSPs
* A method for PSPs to make a **proxy resolution request** to the proxy directory (ie sending a proxy and receiving back a Financial Institution Identification, Account Identification and name of the account holder)

{% hint style="info" %}
In many countries (but not all), the PDO is the same entity as the Instant Payment System Operator (IPSO), and therefore the instant payment *scheme* and proxy resolution *scheme* are managed by the same entity, and the PDO and IPSO are the same entity.
{% endhint %}