Push Pull Notifications API
| Date | Amount |
|---|---|
| Version and status | |
| Available in Sandbox | Yes |
| Sandbox base URL | https://test-api.service.hmrc.gov.uk |
| Available in Production | Yes |
| Production base URL | https://api.service.hmrc.gov.uk |
Overview
Use the Push Pull Notifications API to get notifications (pull) and to send notifications (push) automatically.
Other HMRC APIs create notifications in response to events like asynchronous API requests.
Check if the HMRC API you are using supports Push Pull Notifications in the API documentation.
Notifications will be deleted after 30 days.
Push notifications
You can enter a Push/Callback URL after subscribing to an HMRC API that supports Push Pull Notifications.
Created notifications are sent automatically by a POST request to the Push/Callback URL.
For example, if the Push/Callback URL is set to https://www.example.com/push when a notification is created, a POST
request is sent to https://www.example.com/push with a body similar to:
{
"notificationId": "1ed5f407-8096-40d1-87ef-9a2a103eeb85",
"boxId": "50dca3fc-c37c-4f03-b719-63571333624c",
"messageContentType": "application/json",
"message": "{\"key\":\"value\"}",
"status": "PENDING",
"createdDateTime": "2020-06-01T10:20:23.160+0000"
}
We only support PPNS callback URLs on the default HTTPS port 443. You do not need to specify the port in the callback URL.
See get a list of notifications for details about the structure of this JSON object.
When a notification is pushed its status will be PENDING. If your service responds to this request with an HTTP status code 200, the notification status is updated to ACKNOWLEDGED.
If your service responds with a different HTTP status code, the notification status will remain as PENDING and the request is retried several times over the next few hours.
If after a few hours, an HTTP status code 200 has not been received, the notification status is updated to FAILED.
Validating the callback URL
When you save a callback URL to receive push notifications from an API, the system will try to verify it by sending a GET request to the callback URL with the query parameter “challenge”.
You should return a 200 response with the challenge in the JSON response body. For example:
{
“challenge”: “challenge_from_query_parameter”
}
If we don’t receive a successful response with a matching challenge within 20 seconds, the request to save the callback URL will fail.
You will see an error message to inform you that the callback URL is invalid.
Push Secret
When you subscribe to an API that sends Push notifications, we will generate a push secret you can use to validate the payload signature and confirm notifications come from HMRC.
Validate the payload signature
Using the push secret, HMRC will generate a signature of the payload for every notification sent to the callback URL.
That signature will be available in the HTTP header called X-Hub-Signature.
When receiving a notification, you should compute the signature of the payload using the push secret and verify that it matches the value in the X-Hub-Signature header.
The signature is calculated using HMAC-SHA1 and converted to hexadecimal format. For example (example in Scala)
import java.nio.charset.StandardCharsets.UTF_8
import javax.crypto.Mac
import javax.crypto.spec.SecretKeySpec
def sign(pushSecret: String, payload: String): String = {
val secretKey = new SecretKeySpec(pushSecret.getBytes(UTF_8), "HmacSHA1")
val mac = Mac.getInstance("HmacSHA1")
mac.init(secretKey)
mac.doFinal(payload.getBytes(UTF_8)).map("%02x".format(_)).mkString
}
Using sample key as a pushSecret and {"sample": "payload"} as a payload, will return the signature c6cdd3e30021fe66d88d37088fed2566453eb7fb.
Pull notifications
Regardless of whether a Push/Callback URL is set up, notifications can be retrieved by polling get a list of notifications
Avoid breaking our rate limits and call the endpoint no more than once every 10 seconds.
You will need a Box Identifier to use this endpoint. A Box Identifier is made available by the HMRC API you are using.
When you have successfully processed the notification, you can update its status to ACKNOWLEDGED by calling the
acknowledge a list of notifications endpoint.
Notification statuses
PENDINGmeans the notification was created but has not been processedFAILEDmeans the notification was pushed to your Push/Callback URL, but no HTTP status code 200 was returnedACKNOWLEDGEDmeans the notification was successfully pushed to your Push/Callback URL or you processed the notification using the acknowledge a list of notifications endpoint
Processing notifications
The way to process notifications is different for each HMRC API. Check the documentation for the HMRC API you are using.
Notification messages should include information like a correlation or request identifier that allows notifications to be identified.
Errors
Testing
Versioning
Endpoints
The way we show Push Pull Notifications API v1.0 endpoints has changed, which might look different to other Developer Hub APIs.
The API has not changed. You do not need to make any updates to your application if you already use this API.