diff --git a/src/annotation/index.ts b/src/annotation/index.ts
index 7740b783d..0093af83b 100644
--- a/src/annotation/index.ts
+++ b/src/annotation/index.ts
@@ -1312,6 +1312,20 @@ export class LocalAnnotationSource extends AnnotationSource {
     );
   }
 
+  getUniquePropertyId() {
+    const { properties } = this;
+    const ids = new Set<string>();
+    for (const p of properties.value) {
+      ids.add(p.identifier);
+    }
+    while (true) {
+      const uuid = crypto.randomUUID();
+      if (!ids.has(uuid)) {
+        return uuid;
+      }
+    }
+  }
+
   addProperty(property: AnnotationPropertySpec) {
     this.properties.value.push(property);
     for (const annotation of this) {
diff --git a/src/layer/annotation/index.ts b/src/layer/annotation/index.ts
index 846cad5c8..1ada323a6 100644
--- a/src/layer/annotation/index.ts
+++ b/src/layer/annotation/index.ts
@@ -535,7 +535,7 @@ class TagsTab extends Tab {
                   enumLabels: ["", value],
                   default: 0,
                   description: value,
-                  identifier: self.crypto.randomUUID(), // TODO
+                  identifier: localAnnotations.getUniquePropertyId(),
                 });
               }
             }