diff --git a/src/__tests__/transferWebhook.spec.ts b/src/__tests__/transferWebhook.spec.ts
new file mode 100644
index 000000000..e7fe7b951
--- /dev/null
+++ b/src/__tests__/transferWebhook.spec.ts
@@ -0,0 +1,35 @@
+import BankingWebhookHandler from "../notification/bankingWebhookHandler";
+import { EstimationTrackingData } from "../typings/transferWebhooks/estimationTrackingData";
+
+describe("Transfer Webhook Serialization", (): void => {
+  it("should correctly deserialize union types in transfer webhooks", () => {
+    // Simplest possible webhook with just the fields we need to test
+    const webhookData = {
+      data: {
+        id: "test-transfer-id",
+        tracking: {
+          estimatedArrivalTime: "2025-04-23T22:30:00+02:00",
+          type: "estimation",
+        },
+      },
+      type: "balancePlatform.transfer.updated",
+    };
+
+    const jsonString = JSON.stringify(webhookData);
+    const bankingWebhookHandler = new BankingWebhookHandler(jsonString);
+    const transferNotification =
+      bankingWebhookHandler.getTransferNotificationRequest();
+
+    if (transferNotification.data.tracking?.type === "estimation") {
+      // Verify that the tracking object is properly deserialized to the correct type
+      expect(transferNotification.data.tracking).toBeInstanceOf(
+        EstimationTrackingData
+      );
+
+      // Verify that estimatedArrivalTime is properly converted to a Date object
+      expect(
+        transferNotification.data.tracking.estimatedArrivalTime
+      ).toBeInstanceOf(Date);
+    }
+  });
+});
diff --git a/src/typings/transferWebhooks/models.ts b/src/typings/transferWebhooks/models.ts
index 3527dbef3..dd5962a6a 100644
--- a/src/typings/transferWebhooks/models.ts
+++ b/src/typings/transferWebhooks/models.ts
@@ -259,6 +259,25 @@ export class ObjectSerializer {
                 return expectedType;
             }
 
+            // Handle union types
+            if (expectedType.includes(" | ")) {
+                const unionTypes = expectedType.split(" | ").map((t) => t.trim());
+
+                // For tracking field specifically, use the 'type' field to determine the actual type
+                if (data && data.type && unionTypes.some((t) => t.includes("TrackingData"))) {
+                    if (data.type === "estimation") return "EstimationTrackingData";
+                    if (data.type === "confirmation") return "ConfirmationTrackingData";
+                    if (data.type === "internalReview") return "InternalReviewTrackingData";
+                }
+
+                // For other union types, return the first non-null type that exists in typeMap
+                for (const type of unionTypes) {
+                    if (type !== "null" && typeMap[type]) {
+                        return type;
+                    }
+                }
+            }
+
             if (!typeMap[expectedType]) {
                 return expectedType; // w/e we don't know the type
             }