diff --git a/src/main.ts b/src/main.ts
index 7f3f16cb..7dd22b75 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -408,7 +408,7 @@ export class Purchases {
       rcSource: this._flags.rcSource ?? null,
       workflowContext: this._context?.workflowContext,
     });
-    this.backend = new Backend(this._API_KEY, httpConfig);
+    this.backend = new Backend(this._API_KEY, httpConfig, this._context);
     this.inMemoryCache = new InMemoryCache();
     this.purchaseOperationHelper = new PurchaseOperationHelper(
       this.backend,
diff --git a/src/networking/backend.ts b/src/networking/backend.ts
index a536a94e..ab43e4c7 100644
--- a/src/networking/backend.ts
+++ b/src/networking/backend.ts
@@ -25,6 +25,7 @@ import type {
   PurchaseMetadata,
   PurchaseOption,
 } from "../entities/offerings";
+import type { PurchasesContext } from "../entities/purchases-config";
 import type { CheckoutCompleteResponse } from "./responses/checkout-complete-response";
 import type { CheckoutCalculateTaxResponse } from "./responses/checkout-calculate-tax-response";
 import { SetAttributesEndpoint } from "./endpoints";
@@ -35,11 +36,17 @@ export class Backend {
   private readonly API_KEY: string;
   private readonly httpConfig: HttpConfig;
   private readonly isSandbox: boolean;
+  private readonly purchasesContext?: PurchasesContext;
 
-  constructor(API_KEY: string, httpConfig: HttpConfig = defaultHttpConfig) {
+  constructor(
+    API_KEY: string,
+    httpConfig: HttpConfig = defaultHttpConfig,
+    purchasesContext?: PurchasesContext,
+  ) {
     this.API_KEY = API_KEY;
     this.httpConfig = httpConfig;
     this.isSandbox = isWebBillingSandboxApiKey(API_KEY);
+    this.purchasesContext = purchasesContext;
   }
 
   getIsSandbox(): boolean {
@@ -129,6 +136,7 @@ export class Backend {
       presented_offering_identifier: string;
       price_id: string;
       presented_placement_identifier?: string;
+      presented_workflow_id?: string;
       offer_id?: string;
       applied_targeting_rule?: {
         rule_id: string;
@@ -169,6 +177,11 @@ export class Backend {
         presentedOfferingContext.placementIdentifier;
     }
 
+    if (this.purchasesContext?.workflowContext?.workflowIdentifier) {
+      requestBody.presented_workflow_id =
+        this.purchasesContext.workflowContext.workflowIdentifier;
+    }
+
     return await performRequest<
       CheckoutStartRequestBody,
       CheckoutStartResponse
@@ -299,6 +312,7 @@ export class Backend {
       app_user_id: string;
       presented_offering_identifier: string;
       presented_placement_identifier: string | null;
+      presented_workflow_id?: string | null;
       applied_targeting_rule?: PostReceiptTargetingRule | null;
       initiation_source: string;
     };
@@ -320,6 +334,8 @@ export class Backend {
         presentedOfferingContext.offeringIdentifier,
       presented_placement_identifier:
         presentedOfferingContext.placementIdentifier,
+      presented_workflow_id:
+        this.purchasesContext?.workflowContext?.workflowIdentifier,
       applied_targeting_rule: targetingInfo,
       initiation_source: initiationSource,
     };
diff --git a/src/tests/networking/backend.test.ts b/src/tests/networking/backend.test.ts
index 1eb45c18..c99e8b72 100644
--- a/src/tests/networking/backend.test.ts
+++ b/src/tests/networking/backend.test.ts
@@ -578,6 +578,56 @@ describe("postCheckoutStart request", () => {
     expect(result).toEqual(checkoutStartResponse);
   });
 
+  test("handles workflow identifier correctly", async () => {
+    const backendWithContext = new Backend("test_api_key", undefined, {
+      workflowContext: { workflowIdentifier: "workflow_456" },
+    });
+
+    setCheckoutStartResponse(
+      HttpResponse.json(checkoutStartResponse, { status: 200 }),
+    );
+
+    await backendWithContext.postCheckoutStart(
+      "someAppUserId",
+      "monthly",
+      {
+        offeringIdentifier: "offering_1",
+        targetingContext: null,
+        placementIdentifier: null,
+      },
+      { id: "base_option", priceId: "test_price_id" },
+      "test-trace-id",
+    );
+
+    expect(purchaseMethodAPIMock).toHaveBeenCalledTimes(1);
+    const request = purchaseMethodAPIMock.mock.calls[0][0].request;
+    const requestBody = await request.json();
+    expect(requestBody.presented_workflow_id).toBe("workflow_456");
+  });
+
+  test("omits workflow identifier from request when not present", async () => {
+    setCheckoutStartResponse(
+      HttpResponse.json(checkoutStartResponse, { status: 200 }),
+    );
+
+    await backend.postCheckoutStart(
+      "someAppUserId",
+      "monthly",
+      {
+        offeringIdentifier: "offering_1",
+        targetingContext: null,
+        placementIdentifier: null,
+      },
+      { id: "base_option", priceId: "test_price_id" },
+      "test-trace-id",
+    );
+
+    expect(purchaseMethodAPIMock).toHaveBeenCalledTimes(1);
+    const request = purchaseMethodAPIMock.mock.calls[0][0].request;
+    const requestBody = await request.json();
+    expect(requestBody.presented_workflow_id).toBeUndefined();
+  });
+
   test("throws an error if the backend returns a server error", async () => {
     setCheckoutStartResponse(
       HttpResponse.json(null, { status: StatusCodes.INTERNAL_SERVER_ERROR }),
@@ -1067,6 +1117,56 @@ describe("postReceipt request", () => {
     expect(requestBody.presented_placement_identifier).toBe("home_screen");
   });
 
+  test("handles workflow identifier correctly", async () => {
+    const backendWithContext = new Backend("test_api_key", undefined, {
+      workflowContext: { workflowIdentifier: "workflow_123" },
+    });
+
+    setPostReceiptResponse(
+      HttpResponse.json(customerInfoResponse, { status: 200 }),
+    );
+
+    await backendWithContext.postReceipt(
+      "someAppUserId",
+      "monthly",
+      "EUR",
+      "test_fetch_token",
+      {
+        offeringIdentifier: "offering_1",
+        targetingContext: null,
+        placementIdentifier: null,
+      },
+      "purchase",
+    );
+
+    const request = postReceiptAPIMock.mock.calls[0][0].request;
+    const requestBody = await request.json();
+    expect(requestBody.presented_workflow_id).toBe("workflow_123");
+  });
+
+  test("omits workflow identifier from postReceipt when not present", async () => {
+    setPostReceiptResponse(
+      HttpResponse.json(customerInfoResponse, { status: 200 }),
+    );
+
+    await backend.postReceipt(
+      "someAppUserId",
+      "monthly",
+      "EUR",
+      "test_fetch_token",
+      {
+        offeringIdentifier: "offering_1",
+        targetingContext: null,
+        placementIdentifier: null,
+      },
+      "purchase",
+    );
+
+    const request = postReceiptAPIMock.mock.calls[0][0].request;
+    const requestBody = await request.json();
+    expect(requestBody.presented_workflow_id).toBeUndefined();
+  });
+
   test("throws an error if the backend returns a server error", async () => {
     setPostReceiptResponse(
       HttpResponse.json(null, { status: StatusCodes.INTERNAL_SERVER_ERROR }),