Here are the webhooks that fire for the Form W-9 resource. Since Form W-9s are not filed with a government agency and thus do not go through a life cycle of statuses there is only one webhook event.

Webhook Events

Webhook EventCause
W_9_CREATEDWhen a Form W-9 is successfully created either direct thru the API or via the W-9 Substitute UI Component.

Read more on how to register and validate webhooks here.