---
title: Directories
slug: electronic-prior-auth/guide/directories
docTags: 
createdAt: 2026-06-15T22:01:54.203Z
---

This section explains how directories are used for electronic prior authorization (ePA) message routing. For more detailed information, refer to the *Surescripts Directory Implementation Guide*.

### Provider Vendor Directory Usage

Provider vendors are **not required** to use the Surescripts Directory to identify PBM/payers that support ePA.

However, the Directory **may be used** when:

- An Eligibility Response (271) does not indicate active coverage, and
- The provider still wants to initiate a prior authorization with a specific PBM/payer

In these cases:

- ePA messages are still sent to **EPAINI**
- The **PayerID** in the PAInitiationRequest is populated using the value obtained from the directory

Provider vendors must also ensure that directory service levels are properly configured for prescribers who use ePA.

### PBM/Payer Directory Usage

PBM/payers **do not use the Directory** for routing or message lookup in standard ePA workflows.

- ePA workflows begin with a **PAInitiationRequest sent to EPAINI**
- Responses are sent directly back to the initiating provider vendor
- No directory lookup is required for message routing

**Exception:**

- Unsolicited **PAInitiationResponse** workflows may differ, but standard ePA message exchange does not require PBM/payer directory access