diff --git a/api.planx.uk/modules/file/service/uploadFile.ts b/api.planx.uk/modules/file/service/uploadFile.ts
index d272018c70..ead3cee9af 100644
--- a/api.planx.uk/modules/file/service/uploadFile.ts
+++ b/api.planx.uk/modules/file/service/uploadFile.ts
@@ -7,7 +7,6 @@ import mime from "mime";
 import { customAlphabet } from "nanoid";
 import { isLiveEnv } from "../../../helpers.js";
 import { s3Factory } from "./utils.js";
-import { Readable } from "stream";
 const nanoid = customAlphabet("1234567890abcdefghijklmnopqrstuvwxyz", 8);
 
 export const uploadPublicFile = async (
@@ -29,14 +28,10 @@ export const uploadPublicFile = async (
 };
 
 export const uploadPrivateFile = async (
-  file: Express.Multer.File | Buffer,
+  file: Express.Multer.File,
   filename: string,
   filekey?: string,
 ) => {
-  if (file instanceof Buffer) {
-    file = convertToMulterFile(file);
-  }
-
   const s3 = s3Factory();
 
   const { params, key, fileType } = generateFileParams(file, filename, filekey);
@@ -68,19 +63,6 @@ const buildFileUrl = async (key: string, path: "public" | "private") => {
   return `${process.env.API_URL_EXT}/file/${path}${s3Pathname}`;
 };
 
-const convertToMulterFile = (buffer: Buffer): Express.Multer.File => ({
-  buffer: buffer,
-  originalname: "${data.id}.json",
-  mimetype: "application/json",
-  size: buffer.length,
-  fieldname: "file",
-  encoding: "7bit",
-  stream: Readable.from(buffer),
-  destination: "",
-  filename: "",
-  path: "",
-});
-
 export function generateFileParams(
   file: Express.Multer.File,
   filename: string,
diff --git a/api.planx.uk/modules/file/service/utils.ts b/api.planx.uk/modules/file/service/utils.ts
index 0f95e170e5..85e58cd110 100644
--- a/api.planx.uk/modules/file/service/utils.ts
+++ b/api.planx.uk/modules/file/service/utils.ts
@@ -1,5 +1,6 @@
 import { S3 } from "@aws-sdk/client-s3";
 import { isLiveEnv } from "../../../helpers.js";
+import { Readable } from "stream";
 
 export function s3Factory() {
   return new S3({
@@ -40,3 +41,23 @@ export function getS3KeyFromURL(fileURL: string): string {
   const key = [folder, file].map(decodeURIComponent).join("/");
   return key;
 }
+
+export const convertObjectToMulterJSONFile = (
+  data: Record<string, unknown>,
+  fileName: string,
+): Express.Multer.File => {
+  const buffer = Buffer.from(JSON.stringify(data));
+
+  return {
+    buffer: buffer,
+    originalname: fileName,
+    mimetype: "application/json",
+    size: buffer.length,
+    fieldname: "file",
+    encoding: "7bit",
+    stream: Readable.from(buffer),
+    destination: "",
+    filename: "",
+    path: "",
+  };
+};
diff --git a/api.planx.uk/modules/send/s3/index.ts b/api.planx.uk/modules/send/s3/index.ts
index 8bf46acf5e..d6d8290f8f 100644
--- a/api.planx.uk/modules/send/s3/index.ts
+++ b/api.planx.uk/modules/send/s3/index.ts
@@ -8,10 +8,7 @@ import { uploadPrivateFile } from "../../file/service/uploadFile.js";
 import { markSessionAsSubmitted } from "../../saveAndReturn/service/utils.js";
 import { isApplicationTypeSupported } from "../utils/helpers.js";
 import type { SendIntegrationController } from "../types.js";
-
-// TS fails to validate this complex type when awaited
-// Represent as a simple object to allow enough typechecking to kick in
-type DigitalPlanningPayload = Record<string, unknown>;
+import { convertObjectToMulterJSONFile } from "../../file/service/utils.js";
 
 interface CreateS3Application {
   insertS3Application: {
@@ -49,13 +46,15 @@ const sendToS3: SendIntegrationController = async (_req, res, next) => {
 
     // Generate the ODP Schema JSON, skipping validation if not a supported application type
     const doValidation = isApplicationTypeSupported(passport);
-    const exportData: DigitalPlanningPayload =
-      await $api.export.digitalPlanningDataPayload(sessionId, doValidation);
-
-    const buffer = Buffer.from(JSON.stringify(exportData));
+    const exportData = await $api.export.digitalPlanningDataPayload(
+      sessionId,
+      doValidation,
+    );
 
     // Create and upload the data as an S3 file
-    const { fileUrl } = await uploadPrivateFile(buffer, `${sessionId}.json`);
+    const filename = `${sessionId}.json`;
+    const file = convertObjectToMulterJSONFile(exportData, filename);
+    const { fileUrl } = await uploadPrivateFile(file, filename);
 
     // Send a notification with the file URL to the Power Automate webhook
     const webhookRequest: AxiosRequestConfig = {