In order to offer a future-proven interface for transactions initiated on a physical terminal, Fiserv has introduced the NEXO interface (also called EPAS interface within Fiserv) which is based on the ISO20022 XML standard.

For an Overview about NEXO please refer to nexo-standards.org.

Fiserv supports the following NEXO standards:

• NEXO IS v4.0 provides how to integrate the nexo Specifications and Protocols with a compliant nexo FAST payment application.
• NEXO Acquirer Protocol v6 defines the communication between Terminal connector/host
  and authorization host or card acceptor (in our case: the Fiserv gateway).
• NEXO TMS Protocol defines the framework for configuring, managing and maintaining the application parameters, the software and the security keys of a payment system.
• NEXO Retailer Protocol defines the communication between electronic cashier system
  (ECR) and Terminal connector/host.
• NEXO Fast (3.2) defines processes and workflows, user interaction (such as interfaces and receipt printing) and error handling among the various systems that are involved during payment processing.

This guide focuses on the integration of a POS Host to Fiserv’s payment gateway via NEXO Acquirer Protocol.

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Most important documents that are needed to build the interface on your host:

CAPE - Acceptor to Acquirer - Maintenance 2016 -2017
Message Definition Report - Part 2
(Approved by the ISO 20022 Cards SEG on 10 May 2017)
Download complete message set (external link)

CAPE - Card Payments - Message Usage Guide
Version 6.0 (4 December 2017)
Download the MUG (external link)

nexo-FAST Part 1_V3.2_180528.pdf
Download the NEXO FAST specification (external link)

ISO20022: website of iso20022.org
(NON FISERV) (e.g. for version 6 of the Acquirer protocol)

Within the NEXO archive you will also find other useful resources.

In order to access the NEXO-standards webpage you will need to create a free account.

Messaging

Single vs dual message mode

Fiserv currently only supports single messaging service/mode (SMS, capture in authorization request)

NEXO dual message and batch mode are not supported as of now.

Supported NEXO Cases

The NEXO acquirer message usage guide defines the use cases that terminal vendors need or can implement (See MUG V5.0/6.0, chapter 5.2 and 5.4). Below is a list of the payment cases supported by Fiserv.

Payment Cases

Cancellation Cases

Transaction Types