diff --git a/CHANGELOG.md b/CHANGELOG.md
index 06c61339..cdc3fc6b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@ If you are upgrading from v0.16.x, replace the binary (or run `docker pull`). If
 - DANE: Verify DNSSEC is supported by the resolver before attempting to validate TLSA records.
 - TLS: Update search index when file-backed certificates are refreshed.
 - JMAP: `Principal/query` returns broad results when a `name` or `email` filter cannot be resolved.
+- Webhooks: event IDs collide for same event type emitted in the same second.
 
 ## [0.16.10] - 2026-06-21
 
diff --git a/crates/trc/src/serializers/json.rs b/crates/trc/src/serializers/json.rs
index fed7ff7a..96f79f4e 100644
--- a/crates/trc/src/serializers/json.rs
+++ b/crates/trc/src/serializers/json.rs
@@ -12,6 +12,9 @@ use serde::{
     Serialize, Serializer,
     ser::{SerializeMap, SerializeSeq},
 };
+use std::sync::atomic::{AtomicU64, Ordering};
+
+static EVENT_ID_COUNTER: AtomicU64 = AtomicU64::new(0);
 
 struct Keys<'x> {
     keys: &'x [(Key, Value)],
@@ -83,7 +86,12 @@ impl<T: AsRef<Event<EventDetails>>> Serialize for JsonEventSerializer<T> {
         if self.with_id {
             map.serialize_entry(
                 "id",
-                &format!("{}{}", event.inner.timestamp, event.inner.typ.to_id()),
+                &format!(
+                    "{}{}{}",
+                    event.inner.timestamp,
+                    EVENT_ID_COUNTER.fetch_add(1, Ordering::Relaxed),
+                    event.inner.typ.to_id()
+                ),
             )?;
         }
         if self.with_description {