# Webhooks for custom fields

**URL:** <https://community.servicem8.com/t/webhooks-for-custom-fields/1097>\
**Category:** API & SDK\
**Created:** [May 13, 2026, 4:51am UTC](https://community.servicem8.com/t/webhooks-for-custom-fields/1097 "2026-05-13T04:51:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![integration\_account](https://avatars.discourse-cdn.com/v4/letter/i/9dc877/32.png) [@integration\_account](https://community.servicem8.com/u/integration_account)\
**Post date:** [May 13, 2026, 4:51am UTC](https://community.servicem8.com/t/webhooks-for-custom-fields/1097/1 "2026-05-13T04:51:07Z")

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Hi team,

I’m building an integration using the ServiceM8 API and have created a custom selectlist field on the Job object called “Inspection Approved” (UUID: 173d2179-6a21-4426-a873-242f6421abeb).

I’m trying to subscribe to changes on this field using the Object Webhook endpoint (POST /webhook\_subscriptions/object), but when I pass the field UUID or the field name in the fields parameter, I get the error: “is not a valid field for subscription”.

Could you confirm:

1. Is it possible to subscribe to custom job field changes via the object webhook?
2. If not, is there another recommended way to get notified when a specific custom field value changes on a job without polling?

Thanks

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**Author:** ![Cody](https://sea2.discourse-cdn.com/flex002/user_avatar/community.servicem8.com/cody/32/52_2.png) [@Cody](https://community.servicem8.com/u/Cody)\
**Post date:** [May 16, 2026, 4:53am UTC](https://community.servicem8.com/t/webhooks-for-custom-fields/1097/2 "2026-05-16T04:53:57Z")

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Hi Integration Account,

For object webhooks, the `fields` parameter is a comma-separated list of fields on the object, and a webhook is sent when any of the specified fields change.

Custom fields are commonly used in conjunction with webhooks, and their REST API field name is your `field_name` prefixed with `customfield_` (for example `customfield_favourite_ice_cream`).

Because webhook field subscriptions are defined using API field names, the usual approach is to subscribe to your custom job field using `customfield_<your_field_name>` (you can confirm the `field_name` via `GET /custom_fields_1.0`).

When the webhook fires, the payload only indicates which field(s) changed (it doesn’t include the new value), so you’ll then fetch the Job via the `resource_url` and read the custom field value from the Job record.

If you still can’t get `customfield_<your_field_name>` accepted, the closest “no polling” fallback is subscribing to the `job.updated` event webhook and then retrieving the Job via the REST API to evaluate the custom field value.

If you try the `customfield_` field name and it’s still failing, email [support@servicem8.com](mailto:support@servicem8.com) with the exact subscription request you’re sending and the full error response so we can confirm what’s happening.

Thanks,  
Cody