diff --git a/source/amend_project/configuration/index.html.md.erb b/source/amend_project/configuration/index.html.md.erb
index 9549f8f..669b1ff 100644
--- a/source/amend_project/configuration/index.html.md.erb
+++ b/source/amend_project/configuration/index.html.md.erb
@@ -19,6 +19,14 @@ Tracking ID from Google Analytics
 ga_tracking_id: UA-XXXX-Y
 ```
 
+## `gtm_id`
+
+Google Tag Manager
+
+```yaml
+gtm_id: GTM-XXXX
+```
+
 ## `github_repo`
 
 Your repository. Required if [show_contribution_banner](/amend_project/configuration/#show-contribution-banner) is true.