diff --git a/mod-audit-server/src/test/java/org/folio/services/diff/DiffCalculatorTest.java b/mod-audit-server/src/test/java/org/folio/services/diff/DiffCalculatorTest.java
index 4b2352d1..f897dde9 100644
--- a/mod-audit-server/src/test/java/org/folio/services/diff/DiffCalculatorTest.java
+++ b/mod-audit-server/src/test/java/org/folio/services/diff/DiffCalculatorTest.java
@@ -293,4 +293,4 @@ void shouldDetectFieldChangesInInnerObjectCollectionAndInnerObject() {
   private static Map<String, Object> getMap(Instance obj) {
     return new JsonObject(Json.encode(obj)).getMap();
   }
-}
\ No newline at end of file
+}
diff --git a/mod-audit-server/src/test/java/org/folio/services/diff/HoldingsDiffCalculatorTest.java b/mod-audit-server/src/test/java/org/folio/services/diff/HoldingsDiffCalculatorTest.java
index 50aa4996..25fc8da2 100644
--- a/mod-audit-server/src/test/java/org/folio/services/diff/HoldingsDiffCalculatorTest.java
+++ b/mod-audit-server/src/test/java/org/folio/services/diff/HoldingsDiffCalculatorTest.java
@@ -4,9 +4,13 @@
 
 import io.vertx.core.json.Json;
 import io.vertx.core.json.JsonObject;
+
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Map;
 import org.folio.CopilotGenerated;
 import org.folio.domain.diff.FieldChangeDto;
+import org.folio.rest.external.AdditionalCallNumber;
 import org.folio.rest.external.HoldingsRecord;
 import org.folio.util.inventory.InventoryResourceType;
 import org.folio.utils.UnitTest;
@@ -52,7 +56,32 @@ void shouldDetectFieldModifiedChange() {
       .containsExactlyInAnyOrder(FieldChangeDto.modified("callNumber", "callNumber", "Call Number 1", "Call Number 2"));
   }
 
+  @Test
+  void shouldDetectNewAdditionalCallNumber() {
+    List<AdditionalCallNumber> additionalCallNumberList = new ArrayList<>();
+    AdditionalCallNumber additionalCallNumber = new AdditionalCallNumber().withCallNumber("123").withPrefix("A").withSuffix("Z");
+    additionalCallNumberList.add(additionalCallNumber);
+    var oldItem = getMap(new HoldingsRecord().withId("1").withAdditionalCallNumbers(additionalCallNumberList));
+    AdditionalCallNumber additionalCallNumberNew = new AdditionalCallNumber().withCallNumber("456").withPrefix("A").withSuffix("Z");
+    additionalCallNumberList.add(additionalCallNumberNew);
+    var newItem = getMap(new HoldingsRecord().withId("1").withAdditionalCallNumbers(additionalCallNumberList));
+    var changeRecordDTO = holdingsDiffCalculator.calculateDiff(oldItem, newItem);
+    assertThat(changeRecordDTO.getCollectionChanges()).hasSize(1);
+  }
+
+  @Test
+  void shouldDetectAdditionalCallNumberChange() {
+    List<AdditionalCallNumber> additionalCallNumberList = new ArrayList<>();
+    AdditionalCallNumber additionalCallNumber = new AdditionalCallNumber().withCallNumber("123").withPrefix("A").withSuffix("Z");
+    additionalCallNumberList.add(additionalCallNumber);
+    var oldItem = getMap(new HoldingsRecord().withId("1").withAdditionalCallNumbers(additionalCallNumberList));
+    additionalCallNumberList.getFirst().setCallNumber("456");
+    var newItem = getMap(new HoldingsRecord().withId("1").withAdditionalCallNumbers(additionalCallNumberList));
+    var changeRecordDTO = holdingsDiffCalculator.calculateDiff(oldItem, newItem);
+    assertThat(changeRecordDTO.getCollectionChanges()).hasSize(1);
+  }
+
   private static Map<String, Object> getMap(HoldingsRecord obj) {
     return new JsonObject(Json.encode(obj)).getMap();
   }
-}
\ No newline at end of file
+}
diff --git a/mod-audit-server/src/test/java/org/folio/services/diff/ItemDiffCalculatorTest.java b/mod-audit-server/src/test/java/org/folio/services/diff/ItemDiffCalculatorTest.java
index cfdecc65..9dc35b34 100644
--- a/mod-audit-server/src/test/java/org/folio/services/diff/ItemDiffCalculatorTest.java
+++ b/mod-audit-server/src/test/java/org/folio/services/diff/ItemDiffCalculatorTest.java
@@ -4,9 +4,13 @@
 
 import io.vertx.core.json.Json;
 import io.vertx.core.json.JsonObject;
+
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Map;
 import org.folio.CopilotGenerated;
 import org.folio.domain.diff.FieldChangeDto;
+import org.folio.rest.external.AdditionalCallNumber;
 import org.folio.rest.external.Item;
 import org.folio.util.inventory.InventoryResourceType;
 import org.folio.utils.UnitTest;
@@ -54,7 +58,32 @@ void shouldDetectFieldModifiedChange() {
       .containsExactlyInAnyOrder(FieldChangeDto.modified("barcode", "barcode", "Barcode 1", "Barcode 2"));
   }
 
+  @Test
+  void shouldDetectNewAdditionalCallNumber() {
+    List<AdditionalCallNumber> additionalCallNumberList = new ArrayList<>();
+    AdditionalCallNumber additionalCallNumber = new AdditionalCallNumber().withCallNumber("123").withPrefix("A").withSuffix("Z");
+    additionalCallNumberList.add(additionalCallNumber);
+    var oldItem = getMap(new Item().withId("1").withAdditionalCallNumbers(additionalCallNumberList));
+    AdditionalCallNumber additionalCallNumberNew = new AdditionalCallNumber().withCallNumber("456").withPrefix("A").withSuffix("Z");
+    additionalCallNumberList.add(additionalCallNumberNew);
+    var newItem = getMap(new Item().withId("1").withAdditionalCallNumbers(additionalCallNumberList));
+    var changeRecordDTO = itemDiffCalculator.calculateDiff(oldItem, newItem);
+    assertThat(changeRecordDTO.getCollectionChanges()).hasSize(1);
+  }
+
+  @Test
+  void shouldDetectAdditionalCallNumberChange() {
+    List<AdditionalCallNumber> additionalCallNumberList = new ArrayList<>();
+    AdditionalCallNumber additionalCallNumber = new AdditionalCallNumber().withCallNumber("123").withPrefix("A").withSuffix("Z");
+    additionalCallNumberList.add(additionalCallNumber);
+    var oldItem = getMap(new Item().withId("1").withAdditionalCallNumbers(additionalCallNumberList));
+    additionalCallNumberList.getFirst().setCallNumber("456");
+    var newItem = getMap(new Item().withId("1").withAdditionalCallNumbers(additionalCallNumberList));
+    var changeRecordDTO = itemDiffCalculator.calculateDiff(oldItem, newItem);
+    assertThat(changeRecordDTO.getCollectionChanges()).hasSize(1);
+  }
+
   private static Map<String, Object> getMap(Item obj) {
     return new JsonObject(Json.encode(obj)).getMap();
   }
-}
\ No newline at end of file
+}
diff --git a/ramls/schemas/external/additionalCallNumber.json b/ramls/schemas/external/additionalCallNumber.json
new file mode 100644
index 00000000..3d81d551
--- /dev/null
+++ b/ramls/schemas/external/additionalCallNumber.json
@@ -0,0 +1,20 @@
+{
+  "$schema": "http://json-schema.org/draft-04/schema#",
+  "description": "An additional call number",
+  "type": "object",
+  "properties": {
+    "typeId": {
+      "type": "string"
+    },
+    "prefix": {
+      "type": "string"
+    },
+    "callNumber": {
+      "type": "string"
+    },
+    "suffix": {
+      "type": "string"
+    }
+  },
+  "required": ["callNumber"]
+}
diff --git a/ramls/schemas/external/holdingsRecord.json b/ramls/schemas/external/holdingsRecord.json
index 04f72041..c63a03ff 100644
--- a/ramls/schemas/external/holdingsRecord.json
+++ b/ramls/schemas/external/holdingsRecord.json
@@ -25,6 +25,14 @@
     "callNumberTypeId": {
       "type": "string"
     },
+    "additionalCallNumbers": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "$ref": "additionalCallNumber.json",
+        "uniqueItems": true
+      }
+    },
     "copyNumber": {
       "type": "string"
     },
diff --git a/ramls/schemas/external/item.json b/ramls/schemas/external/item.json
index 457e883d..541c2bce 100644
--- a/ramls/schemas/external/item.json
+++ b/ramls/schemas/external/item.json
@@ -155,6 +155,14 @@
     "itemLevelCallNumberTypeId": {
       "type": "string"
     },
+    "additionalCallNumbers": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "$ref": "additionalCallNumber.json",
+        "uniqueItems": true
+      }
+    },
     "lastCheckIn": {
       "properties": {
         "dateTime": {