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National Event Management Service - FHIR API

Publish and subscribe to patient-centric healthcare event messages with the National Events Management Service (NEMS) - FHIR API.  This national service is implemented on the NHS Spine. 


Sending System
Sending System
publish event
publish event
send event to all
subscribing systems
send event to all...
System B
System A
System C
manage subscriptions
manage subscriptions
Text is not SVG - cannot display How to publish and subscribe to patient-centric healthcare event messages using NEMS and MESH APIs.


Use this API to publish and subscribe to patient-centric healthcare event messages with the National Events Management Service (NEMS).  This national service is implemented on the NHS Spine.

As a sending system, you can:

  • publish an event message

As a subscribing system, you can:

  • create a subscription
  • read a subscription 
  • delete a subscription

This API uses a publish-subscribe model - the sending system publishes specific range of healthcare event messages to National Events Management Service (NEMS), and NEMS forwards the events to all subscribed systems via MESH.

NEMS authorises a specific list of system suppliers and health and social care organisations to publish information as events.

For more details, see the Introduction to the National Events Management Service.

Who can use this

This API can only be used where there is a legal basis to do so.

Make sure you have a valid use case before you go too far with your development. To do this, contact us

For details of the legal basis for sharing NEMS healthcare events, see the NEMS controller catalogue.

You must do this before you can go live (see 'Onboarding' below).


This API is in production.

Service level

This API is a bronze service, meaning it is operational and supported only during business hours (8am to 6pm), Monday to Friday excluding bank holidays.

For more details, see service levels.


This API is a publish-subscribe event API .

All endpoints use FHIR, specifically FHIR STU3, and:

  • the subscription endpoints use RESTful FHIR 
  • the publish endpoint uses FHIR messaging

To collect events that you have subscribed to, use our MESH API.

The message payload is also FHIR - the same format as used by the sending system.

Network access

This API is available on the internet and on the Health and Social Care Network (HSCN).

For more details see Network access for APIs.

Security and authorisation

This API is application-restricted, meaning the calling application is authenticated but the end user is either not authenticated or not present.

In particular, this API uses TLS-MA authentication.

It also implements authorisation controls which restrict the event types the connecting application can subscribe to or publish.

For more details, see application-restricted APIs.

Environments and testing

NEMS is available in Opentest for testing of subscribe message formats using the Toolkit Workbench (TKW).

You do not need access to MESH in Opentest for NEMS testing in Opentest.

Successful validation of subscribe messages in Opentest allows you to proceed to integration testing. For details, see the NEMS onboarding guide.

NEMS is also available for testing purposes in:

  • development (DEV)
  • integration (INT)
  • deployment (DEP)

The base URLs are as follows:

Environment Network availability URL
OpenTest OpenVPN
Development HSCN
Integration HSCN
Integration Internet
Deployment HSCN
Production HSCN Contact us
Production Internet Contact us

The base URL for the publishing and subscribing interactions are the same, but the path is different, for example:

  • publish in integration over HSCN:$process-message
  • subscribe in integration over HSCN:
  • publish in integration over the internet:$process-message
  • subscribe in integration over the internet:

There is a testing tool which allows you to simulate a provider publishing event messages. You can also simulate making changes on PDS to trigger PDS-published event messages so you can test event message consumption.

To get advice on how to begin testing, contact us.

For more details on getting access to test environments, see the NEMS onboarding guide.


You must get your software onboarded before it can go live.

As part of onboarding, this API uses the Supplier Conformance Assessment List (SCAL) process.

For full details, including downloading the NEMS onboarding guide, see onboarding and assurance.


For a full list of interactions for this API , see Publish an Event Message and Subscriptions Overview.

For details on the general structure of the interactions, see FHIR.

Last edited: 11 April 2023 5:33 pm