diff --git a/infrastructure/terraform/components/api/README.md b/infrastructure/terraform/components/api/README.md
index 75faa887f..c346bf431 100644
--- a/infrastructure/terraform/components/api/README.md
+++ b/infrastructure/terraform/components/api/README.md
@@ -43,6 +43,8 @@ No requirements.
 
 | Name | Source | Version |
 |------|--------|---------|
+| <a name="module_amendment_event_transformer"></a> [amendment\_event\_transformer](#module\_amendment\_event\_transformer) | https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.29/terraform-lambda.zip | n/a |
+| <a name="module_amendments_queue"></a> [amendments\_queue](#module\_amendments\_queue) | https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.24/terraform-sqs.zip | n/a |
 | <a name="module_authorizer_lambda"></a> [authorizer\_lambda](#module\_authorizer\_lambda) | https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.29/terraform-lambda.zip | n/a |
 | <a name="module_domain_truststore"></a> [domain\_truststore](#module\_domain\_truststore) | https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.26/terraform-s3bucket.zip | n/a |
 | <a name="module_eventpub"></a> [eventpub](#module\_eventpub) | https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.31/terraform-eventpub.zip | n/a |
@@ -52,7 +54,6 @@ No requirements.
 | <a name="module_get_letters"></a> [get\_letters](#module\_get\_letters) | https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.29/terraform-lambda.zip | n/a |
 | <a name="module_get_status"></a> [get\_status](#module\_get\_status) | https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.29/terraform-lambda.zip | n/a |
 | <a name="module_kms"></a> [kms](#module\_kms) | https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.26/terraform-kms.zip | n/a |
-| <a name="module_letter_status_update"></a> [letter\_status\_update](#module\_letter\_status\_update) | https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.29/terraform-lambda.zip | n/a |
 | <a name="module_letter_status_updates_queue"></a> [letter\_status\_updates\_queue](#module\_letter\_status\_updates\_queue) | https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.24/terraform-sqs.zip | n/a |
 | <a name="module_letter_updates_transformer"></a> [letter\_updates\_transformer](#module\_letter\_updates\_transformer) | https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.29/terraform-lambda.zip | n/a |
 | <a name="module_logging_bucket"></a> [logging\_bucket](#module\_logging\_bucket) | https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.26/terraform-s3bucket.zip | n/a |
diff --git a/infrastructure/terraform/components/api/event_source_mapping_status_updates_to_handler.tf b/infrastructure/terraform/components/api/event_source_mapping_status_updates_to_handler.tf
index ab3634c43..71ecd8085 100644
--- a/infrastructure/terraform/components/api/event_source_mapping_status_updates_to_handler.tf
+++ b/infrastructure/terraform/components/api/event_source_mapping_status_updates_to_handler.tf
@@ -1,12 +1,12 @@
 resource "aws_lambda_event_source_mapping" "status_updates_sqs_to_status_update_handler" {
-  event_source_arn                   = module.letter_status_updates_queue.sqs_queue_arn
-  function_name                      = module.letter_status_update.function_arn
+  event_source_arn                   = module.amendments_queue.sqs_queue_arn
+  function_name                      = module.amendment_event_transformer.function_arn
   batch_size                         = 10
   maximum_batching_window_in_seconds = 1
   scaling_config { maximum_concurrency = 10 }
 
   depends_on = [
-    module.letter_status_updates_queue, # ensures queue exists
-    module.letter_status_update         # ensures update handler exists
+    module.amendments_queue,           # ensures queue exists
+    module.amendment_event_transformer # ensures update handler exists
   ]
 }
diff --git a/infrastructure/terraform/components/api/lambda_event_source_mapping_amendments.tf b/infrastructure/terraform/components/api/lambda_event_source_mapping_amendments.tf
new file mode 100644
index 000000000..ffbf4bf8e
--- /dev/null
+++ b/infrastructure/terraform/components/api/lambda_event_source_mapping_amendments.tf
@@ -0,0 +1,9 @@
+resource "aws_lambda_event_source_mapping" "amendment_event_transformer" {
+  event_source_arn                   = module.amendments_queue.sqs_queue_arn
+  function_name                      = module.amendment_event_transformer.function_name
+  batch_size                         = 10
+  maximum_batching_window_in_seconds = 5
+  function_response_types = [
+    "ReportBatchItemFailures"
+  ]
+}
diff --git a/infrastructure/terraform/components/api/lambda_event_source_mapping_letter_status_update.tf b/infrastructure/terraform/components/api/lambda_event_source_mapping_letter_status_update.tf
new file mode 100644
index 000000000..5813b8e3d
--- /dev/null
+++ b/infrastructure/terraform/components/api/lambda_event_source_mapping_letter_status_update.tf
@@ -0,0 +1,9 @@
+resource "aws_lambda_event_source_mapping" "letter_status_update" {
+  event_source_arn                   = module.letter_status_updates_queue.sqs_queue_arn
+  function_name                      = module.amendment_event_transformer.function_name
+  batch_size                         = 10
+  maximum_batching_window_in_seconds = 5
+  function_response_types = [
+    "ReportBatchItemFailures"
+  ]
+}
diff --git a/infrastructure/terraform/components/api/locals.tf b/infrastructure/terraform/components/api/locals.tf
index 72ae70ba6..46c7aca72 100644
--- a/infrastructure/terraform/components/api/locals.tf
+++ b/infrastructure/terraform/components/api/locals.tf
@@ -27,6 +27,8 @@ locals {
     SUPPLIER_ID_HEADER       = "nhsd-supplier-id",
     APIM_CORRELATION_HEADER  = "nhsd-correlation-id",
     DOWNLOAD_URL_TTL_SECONDS = 60
+    SNS_TOPIC_ARN            = "${module.eventsub.sns_topic.arn}",
+    EVENT_SOURCE             = "/data-plane/supplier-api/${var.group}/${var.environment}/letters"
   }
 
   core_pdf_bucket_arn        = "arn:aws:s3:::comms-${var.core_account_id}-eu-west-2-${var.core_environment}-api-stg-pdf-pipeline"
diff --git a/infrastructure/terraform/components/api/module_lambda_letter_status_update.tf b/infrastructure/terraform/components/api/module_lambda_amendment_event_transformer.tf
similarity index 76%
rename from infrastructure/terraform/components/api/module_lambda_letter_status_update.tf
rename to infrastructure/terraform/components/api/module_lambda_amendment_event_transformer.tf
index b9d97fec5..d26d6d4f6 100644
--- a/infrastructure/terraform/components/api/module_lambda_letter_status_update.tf
+++ b/infrastructure/terraform/components/api/module_lambda_amendment_event_transformer.tf
@@ -1,7 +1,7 @@
-module "letter_status_update" {
+module "amendment_event_transformer" {
   source = "https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.29/terraform-lambda.zip"
 
-  function_name = "letter_status_update"
+  function_name = "amendment_event_transformer"
   description   = "Processes letter status updates"
 
   aws_account_id = var.aws_account_id
@@ -15,14 +15,14 @@ module "letter_status_update" {
   kms_key_arn           = module.kms.key_arn
 
   iam_policy_document = {
-    body = data.aws_iam_policy_document.letter_status_update.json
+    body = data.aws_iam_policy_document.amendment_event_transformer.json
   }
 
   function_s3_bucket      = local.acct.s3_buckets["lambda_function_artefacts"]["id"]
   function_code_base_path = local.aws_lambda_functions_dir_path
   function_code_dir       = "api-handler/dist"
   function_include_common = true
-  handler_function_name   = "letterStatusUpdate"
+  handler_function_name   = "transformAmendmentEvent"
   runtime                 = "nodejs22.x"
   memory                  = 512
   timeout                 = 29
@@ -37,7 +37,7 @@ module "letter_status_update" {
   lambda_env_vars = merge(local.common_lambda_env_vars, {})
 }
 
-data "aws_iam_policy_document" "letter_status_update" {
+data "aws_iam_policy_document" "amendment_event_transformer" {
   statement {
     sid    = "KMSPermissions"
     effect = "Allow"
@@ -59,7 +59,6 @@ data "aws_iam_policy_document" "letter_status_update" {
     actions = [
       "dynamodb:GetItem",
       "dynamodb:Query",
-      "dynamodb:UpdateItem",
     ]
 
     resources = [
@@ -79,7 +78,21 @@ data "aws_iam_policy_document" "letter_status_update" {
     ]
 
     resources = [
-      module.letter_status_updates_queue.sqs_queue_arn
+      module.letter_status_updates_queue.sqs_queue_arn,
+      module.amendments_queue.sqs_queue_arn,
+    ]
+  }
+
+  statement {
+    sid    = "AllowSNSPublish"
+    effect = "Allow"
+
+    actions = [
+      "sns:Publish"
+    ]
+
+    resources = [
+      module.eventsub.sns_topic.arn
     ]
   }
 }
diff --git a/infrastructure/terraform/components/api/module_lambda_patch_letter.tf b/infrastructure/terraform/components/api/module_lambda_patch_letter.tf
index d10e8f240..0298e0887 100644
--- a/infrastructure/terraform/components/api/module_lambda_patch_letter.tf
+++ b/infrastructure/terraform/components/api/module_lambda_patch_letter.tf
@@ -35,7 +35,7 @@ module "patch_letter" {
   log_subscription_role_arn = local.acct.log_subscription_role_arn
 
   lambda_env_vars = merge(local.common_lambda_env_vars, {
-    QUEUE_URL = module.letter_status_updates_queue.sqs_queue_url
+    QUEUE_URL = module.amendments_queue.sqs_queue_url
   })
 }
 
@@ -64,7 +64,7 @@ data "aws_iam_policy_document" "patch_letter_lambda" {
     ]
 
     resources = [
-      module.letter_status_updates_queue.sqs_queue_arn
+      module.amendments_queue.sqs_queue_arn
     ]
   }
 }
diff --git a/infrastructure/terraform/components/api/module_lambda_post_letters.tf b/infrastructure/terraform/components/api/module_lambda_post_letters.tf
index 79b3b3f0b..55865da34 100644
--- a/infrastructure/terraform/components/api/module_lambda_post_letters.tf
+++ b/infrastructure/terraform/components/api/module_lambda_post_letters.tf
@@ -35,7 +35,7 @@ module "post_letters" {
   log_subscription_role_arn = local.acct.log_subscription_role_arn
 
   lambda_env_vars = merge(local.common_lambda_env_vars, {
-    QUEUE_URL = module.letter_status_updates_queue.sqs_queue_url,
+    QUEUE_URL = module.amendments_queue.sqs_queue_url,
     MAX_LIMIT = var.max_get_limit
   })
 }
@@ -65,7 +65,7 @@ data "aws_iam_policy_document" "post_letters" {
     ]
 
     resources = [
-      module.letter_status_updates_queue.sqs_queue_arn
+      module.amendments_queue.sqs_queue_arn
     ]
   }
 }
diff --git a/infrastructure/terraform/components/api/module_sqs_amendments.tf b/infrastructure/terraform/components/api/module_sqs_amendments.tf
new file mode 100644
index 000000000..264441e55
--- /dev/null
+++ b/infrastructure/terraform/components/api/module_sqs_amendments.tf
@@ -0,0 +1,16 @@
+# Queue to transport letter status amendment messages
+module "amendments_queue" {
+  source = "https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.24/terraform-sqs.zip"
+
+  name = "amendments_queue"
+
+  aws_account_id = var.aws_account_id
+  component      = var.component
+  environment    = var.environment
+  project        = var.project
+  region         = var.region
+
+  sqs_kms_key_arn = module.kms.key_arn
+
+  create_dlq = true
+}
diff --git a/infrastructure/terraform/components/api/module_sqs_letter_status_updates.tf b/infrastructure/terraform/components/api/module_sqs_letter_status_updates.tf
index a604faaf5..4d2c581b1 100644
--- a/infrastructure/terraform/components/api/module_sqs_letter_status_updates.tf
+++ b/infrastructure/terraform/components/api/module_sqs_letter_status_updates.tf
@@ -1,4 +1,5 @@
-# Queue to transport update letter status messages
+# Queue to transport update letter status messages. Now replaced by module.amendments_queue.
+# This queue will not be removed just yet, to allow it to be drained following the release in which module.amendments_queue replaces it.
 module "letter_status_updates_queue" {
   source = "https://github.com/NHSDigital/nhs-notify-shared-modules/releases/download/v2.0.24/terraform-sqs.zip"
 
diff --git a/internal/datastore/src/__test__/letter-repository.test.ts b/internal/datastore/src/__test__/letter-repository.test.ts
index 4c44ddbe6..193c1c077 100644
--- a/internal/datastore/src/__test__/letter-repository.test.ts
+++ b/internal/datastore/src/__test__/letter-repository.test.ts
@@ -14,10 +14,12 @@ function createLetter(
   supplierId: string,
   letterId: string,
   status: Letter["status"] = "PENDING",
+  eventId?: string,
 ): InsertLetter {
   const now = new Date().toISOString();
   return {
     id: letterId,
+    eventId,
     supplierId,
     specificationId: "specification1",
     groupId: "group1",
@@ -168,6 +170,7 @@ describe("LetterRepository", () => {
 
     const updateLetter: UpdateLetter = {
       id: "letter1",
+      eventId: "event1",
       supplierId: "supplier1",
       status: "REJECTED",
       reasonCode: "R01",
@@ -180,6 +183,7 @@ describe("LetterRepository", () => {
       "letter1",
     );
     expect(updatedLetter.status).toBe("REJECTED");
+    expect(updatedLetter.previousStatus).toBe("PENDING");
     expect(updatedLetter.reasonCode).toBe("R01");
     expect(updatedLetter.reasonText).toBe("Reason text");
   });
@@ -199,6 +203,7 @@ describe("LetterRepository", () => {
     jest.setSystemTime(new Date(2020, 1, 2));
     const letterDto: UpdateLetter = {
       id: "letter1",
+      eventId: "event1",
       supplierId: "supplier1",
       status: "DELIVERED",
     };
@@ -215,6 +220,7 @@ describe("LetterRepository", () => {
   test("can't update a letter that does not exist", async () => {
     const updateLetter: UpdateLetter = {
       id: "letter1",
+      eventId: "event1",
       supplierId: "supplier1",
       status: "DELIVERED",
     };
@@ -233,6 +239,7 @@ describe("LetterRepository", () => {
 
     const updateLetter: UpdateLetter = {
       id: "letter1",
+      eventId: "event1",
       supplierId: "supplier1",
       status: "DELIVERED",
     };
@@ -241,6 +248,52 @@ describe("LetterRepository", () => {
     ).rejects.toThrow("Cannot do operations on a non-existent table");
   });
 
+  test("does not update a letter if the same eventId is used", async () => {
+    const letter = createLetter("supplier1", "letter1", "DELIVERED", "event1");
+    await letterRepository.putLetter(letter);
+
+    const duplicateUpdate: UpdateLetter = {
+      id: "letter1",
+      eventId: "event1",
+      supplierId: "supplier1",
+      status: "REJECTED",
+      reasonCode: "R01",
+    };
+    const result = await letterRepository.updateLetterStatus(duplicateUpdate);
+
+    expect(result).toBeUndefined();
+    const unchangedLetter = await letterRepository.getLetterById(
+      "supplier1",
+      "letter1",
+    );
+    expect(unchangedLetter.status).toBe("DELIVERED");
+    expect(unchangedLetter.eventId).toBe("event1");
+    expect(unchangedLetter.reasonCode).toBeUndefined();
+  });
+
+  test("updates a letter if a different eventId is used", async () => {
+    const letter = createLetter("supplier1", "letter1", "DELIVERED", "event1");
+    await letterRepository.putLetter(letter);
+
+    const duplicateUpdate: UpdateLetter = {
+      id: "letter1",
+      eventId: "event2",
+      supplierId: "supplier1",
+      status: "REJECTED",
+      reasonCode: "R01",
+    };
+    const result = await letterRepository.updateLetterStatus(duplicateUpdate);
+
+    expect(result).toBeDefined();
+    const changedLetter = await letterRepository.getLetterById(
+      "supplier1",
+      "letter1",
+    );
+    expect(changedLetter.status).toBe("REJECTED");
+    expect(changedLetter.eventId).toBe("event2");
+    expect(changedLetter.reasonCode).toBe("R01");
+  });
+
   test("should return a list of letters matching status", async () => {
     await letterRepository.putLetter(createLetter("supplier1", "letter1"));
     await letterRepository.putLetter(createLetter("supplier1", "letter2"));
@@ -278,6 +331,7 @@ describe("LetterRepository", () => {
 
     const updateLetter: UpdateLetter = {
       id: "letter1",
+      eventId: "event1",
       supplierId: "supplier1",
       status: "DELIVERED",
     };
diff --git a/internal/datastore/src/letter-repository.ts b/internal/datastore/src/letter-repository.ts
index f22868789..def7c1b36 100644
--- a/internal/datastore/src/letter-repository.ts
+++ b/internal/datastore/src/letter-repository.ts
@@ -7,6 +7,7 @@ import {
   UpdateCommand,
   UpdateCommandOutput,
 } from "@aws-sdk/lib-dynamodb";
+import { ConditionalCheckFailedException } from "@aws-sdk/client-dynamodb";
 import { Logger } from "pino";
 import { z } from "zod";
 import {
@@ -163,32 +164,16 @@ export class LetterRepository {
     };
   }
 
-  async updateLetterStatus(letterToUpdate: UpdateLetter): Promise<Letter> {
+  async updateLetterStatus(
+    letterToUpdate: UpdateLetter,
+  ): Promise<Letter | undefined> {
     this.log.debug(
       `Updating letter ${letterToUpdate.id} to status ${letterToUpdate.status}`,
     );
     let result: UpdateCommandOutput;
     try {
-      let updateExpression =
-        "set #status = :status, updatedAt = :updatedAt, supplierStatus = :supplierStatus, #ttl = :ttl";
-      const expressionAttributeValues: Record<string, any> = {
-        ":status": letterToUpdate.status,
-        ":updatedAt": new Date().toISOString(),
-        ":supplierStatus": `${letterToUpdate.supplierId}#${letterToUpdate.status}`,
-        ":ttl": Math.floor(
-          Date.now() / 1000 + 60 * 60 * this.config.lettersTtlHours,
-        ),
-      };
-
-      if (letterToUpdate.reasonCode) {
-        updateExpression += ", reasonCode = :reasonCode";
-        expressionAttributeValues[":reasonCode"] = letterToUpdate.reasonCode;
-      }
-
-      if (letterToUpdate.reasonText) {
-        updateExpression += ", reasonText = :reasonText";
-        expressionAttributeValues[":reasonText"] = letterToUpdate.reasonText;
-      }
+      const { expressionAttributeValues, updateExpression } =
+        this.buildUpdateExpression(letterToUpdate);
 
       result = await this.ddbClient.send(
         new UpdateCommand({
@@ -198,31 +183,61 @@ export class LetterRepository {
             supplierId: letterToUpdate.supplierId,
           },
           UpdateExpression: updateExpression,
-          ConditionExpression: "attribute_exists(id)", // Ensure letter exists
+          ConditionExpression:
+            "attribute_exists(id) AND (attribute_not_exists(eventId) OR eventId <> :eventId)",
           ExpressionAttributeNames: {
             "#status": "status",
             "#ttl": "ttl",
           },
           ExpressionAttributeValues: expressionAttributeValues,
           ReturnValues: "ALL_NEW",
+          ReturnValuesOnConditionCheckFailure: "ALL_OLD",
         }),
       );
+
+      this.log.debug(
+        `Updated letter ${letterToUpdate.id} to status ${letterToUpdate.status}`,
+      );
+      return LetterSchema.parse(result.Attributes);
     } catch (error) {
-      if (
-        error instanceof Error &&
-        error.name === "ConditionalCheckFailedException"
-      ) {
+      if (error instanceof ConditionalCheckFailedException) {
+        if (error.Item?.eventId.S === letterToUpdate.eventId) {
+          this.log.warn(
+            `Skipping update for letter ${letterToUpdate.id}: eventId ${letterToUpdate.eventId} already processed`,
+          );
+          return undefined;
+        }
         throw new Error(
           `Letter with id ${letterToUpdate.id} not found for supplier ${letterToUpdate.supplierId}`,
         );
       }
       throw error;
     }
+  }
 
-    this.log.debug(
-      `Updated letter ${letterToUpdate.id} to status ${letterToUpdate.status}`,
-    );
-    return LetterSchema.parse(result.Attributes);
+  private buildUpdateExpression(letterToUpdate: UpdateLetter) {
+    let updateExpression = `set #status = :status, previousStatus = #status, updatedAt = :updatedAt, supplierStatus = :supplierStatus,
+                                #ttl = :ttl, eventId = :eventId`;
+    const expressionAttributeValues: Record<string, any> = {
+      ":status": letterToUpdate.status,
+      ":updatedAt": new Date().toISOString(),
+      ":supplierStatus": `${letterToUpdate.supplierId}#${letterToUpdate.status}`,
+      ":ttl": Math.floor(
+        Date.now() / 1000 + 60 * 60 * this.config.lettersTtlHours,
+      ),
+      ":eventId": letterToUpdate.eventId,
+    };
+
+    if (letterToUpdate.reasonCode) {
+      updateExpression += ", reasonCode = :reasonCode";
+      expressionAttributeValues[":reasonCode"] = letterToUpdate.reasonCode;
+    }
+
+    if (letterToUpdate.reasonText) {
+      updateExpression += ", reasonText = :reasonText";
+      expressionAttributeValues[":reasonText"] = letterToUpdate.reasonText;
+    }
+    return { updateExpression, expressionAttributeValues };
   }
 
   async getLettersBySupplier(
diff --git a/internal/datastore/src/types.ts b/internal/datastore/src/types.ts
index a0b9f719c..fd83e0403 100644
--- a/internal/datastore/src/types.ts
+++ b/internal/datastore/src/types.ts
@@ -42,9 +42,11 @@ export const LetterSchemaBase = z.object({
 
 export const LetterSchema = LetterSchemaBase.extend({
   supplierId: idRef(SupplierSchema, "id"),
+  eventId: z.string().optional(),
   url: z.url(),
   createdAt: z.string(),
   updatedAt: z.string(),
+  previousStatus: LetterStatus.optional(),
   supplierStatus: z.string().describe("Secondary index PK"),
   supplierStatusSk: z.string().describe("Secondary index SK"),
   ttl: z.int(),
@@ -67,6 +69,7 @@ export type InsertLetter = Omit<
 >;
 export type UpdateLetter = {
   id: string;
+  eventId: string;
   supplierId: string;
   status: Letter["status"];
   reasonCode?: string;
diff --git a/internal/events/jest.config.ts b/internal/events/jest.config.ts
index 84251001b..926706a37 100644
--- a/internal/events/jest.config.ts
+++ b/internal/events/jest.config.ts
@@ -24,7 +24,7 @@ export const baseJestConfig: Config = {
     },
   },
 
-  coveragePathIgnorePatterns: ["/__tests__/"],
+  coveragePathIgnorePatterns: ["/src/index.ts$", "/__tests__/"],
   transform: { "^.+\\.ts$": "ts-jest" },
   testPathIgnorePatterns: [".build"],
   testMatch: ["**/?(*.)+(spec|test).[jt]s?(x)"],
diff --git a/internal/events/package.json b/internal/events/package.json
index 40cd8bfcd..4da8a4861 100644
--- a/internal/events/package.json
+++ b/internal/events/package.json
@@ -1,6 +1,7 @@
 {
   "dependencies": {
     "@asyncapi/bundler": "^0.6.4",
+    "@internal/datastore": "*",
     "zod": "^4.1.11"
   },
   "description": "Schemas for NHS Notify Supplier API events",
@@ -50,5 +51,5 @@
     "typecheck": "tsc --noEmit"
   },
   "types": "dist/index.d.ts",
-  "version": "1.0.11"
+  "version": "1.0.12"
 }
diff --git a/internal/events/src/__tests__/version.test.ts b/internal/events/src/__tests__/version.test.ts
new file mode 100644
index 000000000..412eef4ce
--- /dev/null
+++ b/internal/events/src/__tests__/version.test.ts
@@ -0,0 +1,11 @@
+import { MAJOR_VERSION, VERSION } from "../version";
+
+describe("version exports", () => {
+  it("should export MAJOR_VERSION as the first segment of the version", () => {
+    expect(VERSION.startsWith(`${MAJOR_VERSION}.`)).toBeTruthy();
+  });
+
+  it("should have VERSION in semver format", () => {
+    expect(VERSION).toMatch(/^\d+\.\d+\.\d+$/);
+  });
+});
diff --git a/lambdas/letter-updates-transformer/src/mappers/__tests__/letter-mapper.test.ts b/internal/events/src/events/__tests__/letter-mapper.test.ts
similarity index 94%
rename from lambdas/letter-updates-transformer/src/mappers/__tests__/letter-mapper.test.ts
rename to internal/events/src/events/__tests__/letter-mapper.test.ts
index 077d73792..c870dc91b 100644
--- a/lambdas/letter-updates-transformer/src/mappers/__tests__/letter-mapper.test.ts
+++ b/internal/events/src/events/__tests__/letter-mapper.test.ts
@@ -1,6 +1,6 @@
 import { $LetterEvent } from "@nhsdigital/nhs-notify-event-schemas-supplier-api/src";
 import { Letter } from "@internal/datastore";
-import mapLetterToCloudEvent from "../letter-mapper";
+import { mapLetterToCloudEvent } from "@nhsdigital/nhs-notify-event-schemas-supplier-api/src/events/letter-mapper";
 
 describe("letter-mapper", () => {
   it("maps a letter to a letter event", async () => {
diff --git a/lambdas/letter-updates-transformer/src/mappers/letter-mapper.ts b/internal/events/src/events/letter-mapper.ts
similarity index 86%
rename from lambdas/letter-updates-transformer/src/mappers/letter-mapper.ts
rename to internal/events/src/events/letter-mapper.ts
index f2f25a827..91f72988a 100644
--- a/lambdas/letter-updates-transformer/src/mappers/letter-mapper.ts
+++ b/internal/events/src/events/letter-mapper.ts
@@ -1,10 +1,11 @@
-import { LetterEvent } from "@nhsdigital/nhs-notify-event-schemas-supplier-api/src";
 import { randomBytes, randomUUID } from "node:crypto";
 import eventSchemaPackage from "@nhsdigital/nhs-notify-event-schemas-supplier-api/package.json";
-import { LetterForEventPub } from "../types";
+import { Letter } from "@internal/datastore";
+import { LetterEvent } from "./letter-events";
 
-export default function mapLetterToCloudEvent(
-  letter: LetterForEventPub,
+// eslint-disable-next-line import-x/prefer-default-export
+export function mapLetterToCloudEvent(
+  letter: Letter,
   source: string,
 ): LetterEvent {
   const eventId = randomUUID();
diff --git a/internal/events/src/index.ts b/internal/events/src/index.ts
index 339ddcd64..6aecfa516 100644
--- a/internal/events/src/index.ts
+++ b/internal/events/src/index.ts
@@ -4,4 +4,5 @@ export { default as DomainBase } from "./domain/domain-base";
 export * from "./events/event-envelope";
 export * from "./events/letter-events";
 export * from "./events/mi-events";
+export * from "./events/letter-mapper";
 export * from "./version";
diff --git a/internal/events/tsconfig.json b/internal/events/tsconfig.json
index 167e805ad..ad730e287 100644
--- a/internal/events/tsconfig.json
+++ b/internal/events/tsconfig.json
@@ -3,8 +3,7 @@
     "declaration": true,
     "isolatedModules": true,
     "module": "commonjs",
-    "outDir": "dist",
-    "resolveJsonModule": true
+    "outDir": "dist"
   },
   "exclude": [
     "node_modules",
diff --git a/lambdas/api-handler/package.json b/lambdas/api-handler/package.json
index 5bdaf1914..6983976e6 100644
--- a/lambdas/api-handler/package.json
+++ b/lambdas/api-handler/package.json
@@ -2,13 +2,15 @@
   "dependencies": {
     "@aws-sdk/client-dynamodb": "^3.984.0",
     "@aws-sdk/client-s3": "^3.925.0",
+    "@aws-sdk/client-sns": "^3.925.0",
     "@aws-sdk/client-sqs": "^3.925.0",
     "@aws-sdk/lib-dynamodb": "^3.925.0",
     "@aws-sdk/s3-request-presigner": "^3.925.0",
     "@internal/datastore": "*",
     "@internal/helpers": "*",
+    "@nhsdigital/nhs-notify-event-schemas-supplier-api": "*",
     "aws-embedded-metrics": "^4.2.1",
-    "aws-lambda": "^1.0.6",
+    "aws-lambda": "^1.0.7",
     "esbuild": "0.27.2",
     "pino": "^10.3.0",
     "zod": "^4.1.11"
diff --git a/lambdas/api-handler/src/config/__tests__/env.test.ts b/lambdas/api-handler/src/config/__tests__/env.test.ts
index afbca1d82..6b52a3474 100644
--- a/lambdas/api-handler/src/config/__tests__/env.test.ts
+++ b/lambdas/api-handler/src/config/__tests__/env.test.ts
@@ -25,6 +25,8 @@ describe("lambdaEnv", () => {
     process.env.DOWNLOAD_URL_TTL_SECONDS = "60";
     process.env.MAX_LIMIT = "2500";
     process.env.QUEUE_URL = "url";
+    process.env.EVENT_SOURCE = "supplier-api";
+    process.env.SNS_TOPIC_ARN = "sns-topic.arn";
 
     const { envVars } = require("../env");
 
@@ -38,6 +40,8 @@ describe("lambdaEnv", () => {
       DOWNLOAD_URL_TTL_SECONDS: 60,
       MAX_LIMIT: 2500,
       QUEUE_URL: "url",
+      EVENT_SOURCE: "supplier-api",
+      SNS_TOPIC_ARN: "sns-topic.arn",
     });
   });
 
@@ -61,6 +65,8 @@ describe("lambdaEnv", () => {
     process.env.LETTER_TTL_HOURS = "12960";
     process.env.MI_TTL_HOURS = "2160";
     process.env.DOWNLOAD_URL_TTL_SECONDS = "60";
+    process.env.EVENT_SOURCE = "supplier-api";
+    process.env.SNS_TOPIC_ARN = "sns-topic.arn";
 
     const { envVars } = require("../env");
 
@@ -73,6 +79,8 @@ describe("lambdaEnv", () => {
       MI_TTL_HOURS: 2160,
       DOWNLOAD_URL_TTL_SECONDS: 60,
       MAX_LIMIT: undefined,
+      EVENT_SOURCE: "supplier-api",
+      SNS_TOPIC_ARN: "sns-topic.arn",
     });
   });
 });
diff --git a/lambdas/api-handler/src/config/deps.ts b/lambdas/api-handler/src/config/deps.ts
index 1a64998f4..ff4a1020f 100644
--- a/lambdas/api-handler/src/config/deps.ts
+++ b/lambdas/api-handler/src/config/deps.ts
@@ -2,6 +2,7 @@ import { S3Client } from "@aws-sdk/client-s3";
 import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
 import { DynamoDBDocumentClient } from "@aws-sdk/lib-dynamodb";
 import { SQSClient } from "@aws-sdk/client-sqs";
+import { SNSClient } from "@aws-sdk/client-sns";
 import { Logger } from "pino";
 import {
   DBHealthcheck,
@@ -14,6 +15,7 @@ import { EnvVars, envVars } from "./env";
 export type Deps = {
   s3Client: S3Client;
   sqsClient: SQSClient;
+  snsClient: SNSClient;
   letterRepo: LetterRepository;
   miRepo: MIRepository;
   dbHealthcheck: DBHealthcheck;
@@ -62,6 +64,7 @@ export function createDependenciesContainer(): Deps {
   return {
     s3Client: new S3Client(),
     sqsClient: new SQSClient(),
+    snsClient: new SNSClient(),
     letterRepo: createLetterRepository(log, envVars),
     miRepo: createMIRepository(log, envVars),
     dbHealthcheck: createDBHealthcheck(envVars),
diff --git a/lambdas/api-handler/src/config/env.ts b/lambdas/api-handler/src/config/env.ts
index 0a98f2b4d..be22d3182 100644
--- a/lambdas/api-handler/src/config/env.ts
+++ b/lambdas/api-handler/src/config/env.ts
@@ -11,6 +11,8 @@ const EnvVarsSchema = z.object({
   MAX_LIMIT: z.coerce.number().int().optional(),
   QUEUE_URL: z.coerce.string().optional(),
   PINO_LOG_LEVEL: z.coerce.string().optional(),
+  EVENT_SOURCE: z.string(),
+  SNS_TOPIC_ARN: z.string(),
 });
 
 export type EnvVars = z.infer<typeof EnvVarsSchema>;
diff --git a/lambdas/api-handler/src/handlers/__tests__/amendment-event-transformer.test.ts b/lambdas/api-handler/src/handlers/__tests__/amendment-event-transformer.test.ts
new file mode 100644
index 000000000..cce00574c
--- /dev/null
+++ b/lambdas/api-handler/src/handlers/__tests__/amendment-event-transformer.test.ts
@@ -0,0 +1,183 @@
+import { Context, SQSEvent, SQSRecord } from "aws-lambda";
+import { mockDeep } from "jest-mock-extended";
+import pino from "pino";
+import { SNSClient } from "@aws-sdk/client-sns";
+import { mapLetterToCloudEvent } from "@nhsdigital/nhs-notify-event-schemas-supplier-api/src/events/letter-mapper";
+import { Letter, LetterRepository } from "@internal/datastore/src";
+import { UpdateLetterCommand } from "../../contracts/letters";
+import { EnvVars } from "../../config/env";
+import { Deps } from "../../config/deps";
+import createTransformAmendmentEventHandler from "../amendment-event-transformer";
+
+// Make crypto return consistent values, since we"re calling it in both prod and test code and comparing the values
+const realCrypto = jest.requireActual("crypto");
+const randomBytes: Record<string, any> = {
+  "8": realCrypto.randomBytes(8),
+  "16": realCrypto.randomBytes(16),
+};
+jest.mock("crypto", () => ({
+  randomUUID: () => "4616b2d9-b7a5-45aa-8523-fa7419626b69",
+  randomBytes: (size: number) => randomBytes[String(size)],
+}));
+
+const buildEvent = (updateLetterCommand: UpdateLetterCommand[]): SQSEvent => {
+  const records: Partial<SQSRecord>[] = updateLetterCommand.map((letter) => {
+    return {
+      messageId: `mid-${letter.id}`,
+      body: JSON.stringify(letter),
+      messageAttributes: {
+        CorrelationId: {
+          dataType: "String",
+          stringValue: `correlationId-${letter.id}`,
+        },
+      },
+    };
+  });
+
+  const event: Partial<SQSEvent> = {
+    Records: records as SQSRecord[],
+  };
+
+  return event as SQSEvent;
+};
+
+describe("createLetterStatusUpdateHandler", () => {
+  beforeEach(async () => {
+    jest.clearAllMocks();
+  });
+
+  const mockedDeps: jest.Mocked<Deps> = {
+    snsClient: { send: jest.fn() } as unknown as SNSClient,
+    letterRepo: {
+      getLetterById: jest.fn(),
+    } as unknown as LetterRepository,
+    logger: { info: jest.fn(), error: jest.fn() } as unknown as pino.Logger,
+    env: {
+      EVENT_SOURCE: "supplier-api",
+      SNS_TOPIC_ARN: "sns_topic.arn",
+    } as unknown as EnvVars,
+  } as Deps;
+
+  const letters: Letter[] = [
+    {
+      id: "id1",
+      supplierId: "s1",
+      status: "PENDING",
+    } as Letter,
+    {
+      id: "id2",
+      supplierId: "s2",
+      status: "PENDING",
+    } as Letter,
+    {
+      id: "id3",
+      supplierId: "s3",
+      status: "PENDING",
+    } as Letter,
+  ];
+
+  const updateLetterCommands: UpdateLetterCommand[] = [
+    {
+      ...letters[0],
+      status: "REJECTED",
+      reasonCode: "123",
+      reasonText: "Reason text",
+    },
+    { ...letters[1], status: "ACCEPTED" },
+    { ...letters[2], status: "DELIVERED" },
+  ];
+
+  beforeEach(() => {
+    jest.useFakeTimers();
+  });
+
+  afterEach(() => {
+    jest.useRealTimers();
+  });
+
+  it("processes letters successfully", async () => {
+    (mockedDeps.letterRepo.getLetterById as jest.Mock)
+      .mockResolvedValueOnce(letters[0])
+      .mockResolvedValueOnce(letters[1])
+      .mockResolvedValueOnce(letters[2]);
+
+    const context = mockDeep<Context>();
+    const callback = jest.fn();
+
+    const transformAmendmentEventHandler =
+      createTransformAmendmentEventHandler(mockedDeps);
+    await transformAmendmentEventHandler(
+      buildEvent(updateLetterCommands),
+      context,
+      callback,
+    );
+
+    for (let i = 0; i < 3; i++) {
+      expect(mockedDeps.snsClient.send).toHaveBeenNthCalledWith(
+        i + 1,
+        expect.objectContaining({
+          input: expect.objectContaining({
+            TopicArn: mockedDeps.env.SNS_TOPIC_ARN,
+            Message: JSON.stringify(
+              mapLetterToCloudEvent(
+                updateLetterCommands[i] as Letter,
+                mockedDeps.env.EVENT_SOURCE,
+              ),
+            ),
+          }),
+        }),
+      );
+    }
+  });
+
+  it("logs error if error thrown when updating", async () => {
+    const mockError = new Error("Update error");
+    (mockedDeps.snsClient.send as jest.Mock).mockRejectedValue(mockError);
+    (mockedDeps.letterRepo.getLetterById as jest.Mock).mockResolvedValueOnce(
+      letters[1],
+    );
+
+    const context = mockDeep<Context>();
+    const callback = jest.fn();
+
+    const transformAmendmentEventHandler =
+      createTransformAmendmentEventHandler(mockedDeps);
+    await transformAmendmentEventHandler(
+      buildEvent([updateLetterCommands[1]]),
+      context,
+      callback,
+    );
+
+    expect(mockedDeps.logger.error).toHaveBeenCalledWith({
+      description: "Error processing letter status update",
+      err: mockError,
+      messageId: "mid-id2",
+      correlationId: "correlationId-id2",
+      messageBody: '{"id":"id2","supplierId":"s2","status":"ACCEPTED"}',
+    });
+  });
+
+  it("returns batch update failures in the response", async () => {
+    (mockedDeps.letterRepo.getLetterById as jest.Mock)
+      .mockResolvedValueOnce(letters[0])
+      .mockResolvedValueOnce(letters[1])
+      .mockResolvedValueOnce(letters[2]);
+    (mockedDeps.snsClient.send as jest.Mock).mockResolvedValueOnce({});
+    (mockedDeps.snsClient.send as jest.Mock).mockRejectedValueOnce(
+      new Error("Update error"),
+    );
+    (mockedDeps.snsClient.send as jest.Mock).mockResolvedValueOnce({});
+
+    const transformAmendmentEventHandler =
+      createTransformAmendmentEventHandler(mockedDeps);
+    const sqsBatchResponse = await transformAmendmentEventHandler(
+      buildEvent(updateLetterCommands),
+      mockDeep<Context>(),
+      jest.fn(),
+    );
+
+    expect(sqsBatchResponse?.batchItemFailures).toEqual([
+      { itemIdentifier: "mid-id2" },
+    ]);
+  });
+});
diff --git a/lambdas/api-handler/src/handlers/__tests__/letter-status-update.test.ts b/lambdas/api-handler/src/handlers/__tests__/letter-status-update.test.ts
deleted file mode 100644
index 7ec1866b9..000000000
--- a/lambdas/api-handler/src/handlers/__tests__/letter-status-update.test.ts
+++ /dev/null
@@ -1,154 +0,0 @@
-import { Context, SQSEvent, SQSRecord } from "aws-lambda";
-import { mockDeep } from "jest-mock-extended";
-import { S3Client } from "@aws-sdk/client-s3";
-import pino from "pino";
-import { LetterRepository } from "@internal/datastore/src";
-import { UpdateLetterCommand } from "../../contracts/letters";
-import { EnvVars } from "../../config/env";
-import { Deps } from "../../config/deps";
-import createLetterStatusUpdateHandler from "../letter-status-update";
-
-const buildEvent = (updateLetterCommand: UpdateLetterCommand[]): SQSEvent => {
-  const records: Partial<SQSRecord>[] = updateLetterCommand.map((letter) => {
-    return {
-      messageId: `mid-${letter.id}`,
-      body: JSON.stringify(letter),
-      messageAttributes: {
-        CorrelationId: {
-          dataType: "String",
-          stringValue: `correlationId-${letter.id}`,
-        },
-      },
-    };
-  });
-
-  const event: Partial<SQSEvent> = {
-    Records: records as SQSRecord[],
-  };
-
-  return event as SQSEvent;
-};
-
-describe("createLetterStatusUpdateHandler", () => {
-  beforeEach(() => {
-    jest.clearAllMocks();
-  });
-
-  it("processes letters successfully", async () => {
-    const updateLetterCommands: UpdateLetterCommand[] = [
-      {
-        id: "id1",
-        status: "REJECTED",
-        supplierId: "s1",
-        reasonCode: "123",
-        reasonText: "Reason text",
-      },
-      {
-        id: "id2",
-        supplierId: "s2",
-        status: "ACCEPTED",
-      },
-      {
-        id: "id3",
-        supplierId: "s3",
-        status: "DELIVERED",
-      },
-    ];
-
-    const mockedDeps: jest.Mocked<Deps> = {
-      s3Client: {} as unknown as S3Client,
-      letterRepo: {
-        updateLetterStatus: jest
-          .fn()
-          .mockResolvedValueOnce(updateLetterCommands[0])
-          .mockResolvedValueOnce(updateLetterCommands[1])
-          .mockResolvedValueOnce(updateLetterCommands[2]),
-      } as unknown as LetterRepository,
-      logger: { info: jest.fn(), error: jest.fn() } as unknown as pino.Logger,
-      env: {
-        SUPPLIER_ID_HEADER: "nhsd-supplier-id",
-        APIM_CORRELATION_HEADER: "nhsd-correlation-id",
-        LETTERS_TABLE_NAME: "LETTERS_TABLE_NAME",
-        LETTER_TTL_HOURS: 12_960,
-        DOWNLOAD_URL_TTL_SECONDS: 60,
-        MAX_LIMIT: 2500,
-        QUEUE_URL: "SQS_URL",
-      } as unknown as EnvVars,
-    } as Deps;
-
-    const context = mockDeep<Context>();
-    const callback = jest.fn();
-
-    const letterStatusUpdateHandler =
-      createLetterStatusUpdateHandler(mockedDeps);
-    await letterStatusUpdateHandler(
-      buildEvent(updateLetterCommands),
-      context,
-      callback,
-    );
-
-    expect(mockedDeps.letterRepo.updateLetterStatus).toHaveBeenNthCalledWith(
-      1,
-      updateLetterCommands[0],
-    );
-    expect(mockedDeps.letterRepo.updateLetterStatus).toHaveBeenNthCalledWith(
-      2,
-      updateLetterCommands[1],
-    );
-    expect(mockedDeps.letterRepo.updateLetterStatus).toHaveBeenNthCalledWith(
-      3,
-      updateLetterCommands[2],
-    );
-  });
-
-  it("logs error if error thrown when updating", async () => {
-    const mockError = new Error("Update error");
-
-    const mockedDeps: jest.Mocked<Deps> = {
-      s3Client: {} as unknown as S3Client,
-      letterRepo: {
-        updateLetterStatus: jest.fn().mockRejectedValue(mockError),
-      } as unknown as LetterRepository,
-      logger: { info: jest.fn(), error: jest.fn() } as unknown as pino.Logger,
-      env: {
-        SUPPLIER_ID_HEADER: "nhsd-supplier-id",
-        APIM_CORRELATION_HEADER: "nhsd-correlation-id",
-        LETTERS_TABLE_NAME: "LETTERS_TABLE_NAME",
-        LETTER_TTL_HOURS: 12_960,
-        DOWNLOAD_URL_TTL_SECONDS: 60,
-        MAX_LIMIT: 2500,
-        QUEUE_URL: "SQS_URL",
-      } as unknown as EnvVars,
-    } as Deps;
-
-    const context = mockDeep<Context>();
-    const callback = jest.fn();
-
-    const updateLetterCommands: UpdateLetterCommand[] = [
-      {
-        id: "id1",
-        status: "ACCEPTED",
-        supplierId: "s1",
-      },
-    ];
-
-    const letterStatusUpdateHandler =
-      createLetterStatusUpdateHandler(mockedDeps);
-    await letterStatusUpdateHandler(
-      buildEvent(updateLetterCommands),
-      context,
-      callback,
-    );
-
-    expect(mockedDeps.letterRepo.updateLetterStatus).toHaveBeenCalledWith(
-      updateLetterCommands[0],
-    );
-    expect(mockedDeps.logger.error).toHaveBeenCalledWith({
-      description: "Error processing letter status update",
-      err: mockError,
-      messageId: "mid-id1",
-      correlationId: "correlationId-id1",
-      messageBody: '{"id":"id1","status":"ACCEPTED","supplierId":"s1"}',
-    });
-  });
-});
diff --git a/lambdas/api-handler/src/handlers/amendment-event-transformer.ts b/lambdas/api-handler/src/handlers/amendment-event-transformer.ts
new file mode 100644
index 000000000..2ae233332
--- /dev/null
+++ b/lambdas/api-handler/src/handlers/amendment-event-transformer.ts
@@ -0,0 +1,68 @@
+import { SQSBatchItemFailure, SQSEvent, SQSHandler } from "aws-lambda";
+import { PublishCommand } from "@aws-sdk/client-sns";
+import { LetterEvent } from "@nhsdigital/nhs-notify-event-schemas-supplier-api/src/events/letter-events";
+import { mapLetterToCloudEvent } from "@nhsdigital/nhs-notify-event-schemas-supplier-api/src/events/letter-mapper";
+import {
+  UpdateLetterCommand,
+  UpdateLetterCommandSchema,
+} from "../contracts/letters";
+import { Deps } from "../config/deps";
+
+export default function createTransformAmendmentEventHandler(
+  deps: Deps,
+): SQSHandler {
+  return async (event: SQSEvent) => {
+    const batchItemFailures: SQSBatchItemFailure[] = [];
+
+    const tasks = event.Records.map(async (message) => {
+      try {
+        const updateLetterCommand: UpdateLetterCommand =
+          UpdateLetterCommandSchema.parse(JSON.parse(message.body));
+        const letter = await deps.letterRepo.getLetterById(
+          updateLetterCommand.supplierId,
+          updateLetterCommand.id,
+        );
+        letter.status = updateLetterCommand.status;
+        letter.reasonCode = updateLetterCommand.reasonCode;
+        letter.reasonText = updateLetterCommand.reasonText;
+
+        const letterEvent = mapLetterToCloudEvent(
+          letter,
+          deps.env.EVENT_SOURCE,
+        );
+        await deps.snsClient.send(
+          buildSnsCommand(letterEvent, deps.env.SNS_TOPIC_ARN),
+        );
+        deps.logger.info({
+          description: "Sent letter status update via topic",
+          letterId: updateLetterCommand.id,
+          messageId: message.messageId,
+          correlationId: message.messageAttributes.CorrelationId.stringValue,
+        });
+      } catch (error) {
+        deps.logger.error({
+          description: "Error processing letter status update",
+          err: error,
+          messageId: message.messageId,
+          correlationId: message.messageAttributes.CorrelationId.stringValue,
+          messageBody: message.body,
+        });
+        batchItemFailures.push({ itemIdentifier: message.messageId });
+      }
+    });
+
+    await Promise.all(tasks);
+
+    return { batchItemFailures };
+  };
+}
+
+function buildSnsCommand(
+  letterEvent: LetterEvent,
+  topicArn: string,
+): PublishCommand {
+  return new PublishCommand({
+    TopicArn: topicArn,
+    Message: JSON.stringify(letterEvent),
+  });
+}
diff --git a/lambdas/api-handler/src/handlers/letter-status-update.ts b/lambdas/api-handler/src/handlers/letter-status-update.ts
deleted file mode 100644
index b49f8702a..000000000
--- a/lambdas/api-handler/src/handlers/letter-status-update.ts
+++ /dev/null
@@ -1,39 +0,0 @@
-import { SQSEvent, SQSHandler } from "aws-lambda";
-import {
-  UpdateLetterCommand,
-  UpdateLetterCommandSchema,
-} from "../contracts/letters";
-import { Deps } from "../config/deps";
-import { mapToUpdateLetter } from "../mappers/letter-mapper";
-
-export default function createLetterStatusUpdateHandler(
-  deps: Deps,
-): SQSHandler {
-  return async (event: SQSEvent) => {
-    const tasks = event.Records.map(async (message) => {
-      try {
-        const letterToUpdate: UpdateLetterCommand =
-          UpdateLetterCommandSchema.parse(JSON.parse(message.body));
-        await deps.letterRepo.updateLetterStatus(
-          mapToUpdateLetter(letterToUpdate),
-        );
-        deps.logger.info({
-          description: "Updated letter status",
-          letterId: letterToUpdate.id,
-          messageId: message.messageId,
-          correlationId: message.messageAttributes.CorrelationId.stringValue,
-        });
-      } catch (error) {
-        deps.logger.error({
-          description: "Error processing letter status update",
-          err: error,
-          messageId: message.messageId,
-          correlationId: message.messageAttributes.CorrelationId.stringValue,
-          messageBody: message.body,
-        });
-      }
-    });
-
-    await Promise.all(tasks);
-  };
-}
diff --git a/lambdas/api-handler/src/index.ts b/lambdas/api-handler/src/index.ts
index 3a006e48d..573be050d 100644
--- a/lambdas/api-handler/src/index.ts
+++ b/lambdas/api-handler/src/index.ts
@@ -4,7 +4,7 @@ import createGetLetterDataHandler from "./handlers/get-letter-data";
 import createGetLettersHandler from "./handlers/get-letters";
 import createPatchLetterHandler from "./handlers/patch-letter";
 import createPostLettersHandler from "./handlers/post-letters";
-import createLetterStatusUpdateHandler from "./handlers/letter-status-update";
+import createTransformAmendmentEventHandler from "./handlers/amendment-event-transformer";
 import createPostMIHandler from "./handlers/post-mi";
 import createGetStatusHandler from "./handlers/get-status";
 
@@ -14,7 +14,8 @@ export const getLetter = createGetLetterHandler(container);
 export const getLetterData = createGetLetterDataHandler(container);
 export const getLetters = createGetLettersHandler(container);
 export const patchLetter = createPatchLetterHandler(container);
-export const letterStatusUpdate = createLetterStatusUpdateHandler(container);
+export const transformAmendmentEvent =
+  createTransformAmendmentEventHandler(container);
 export const postLetters = createPostLettersHandler(container);
 
 export const postMI = createPostMIHandler(container);
diff --git a/lambdas/api-handler/src/mappers/letter-mapper.ts b/lambdas/api-handler/src/mappers/letter-mapper.ts
index c11d6d8c0..c31d61b34 100644
--- a/lambdas/api-handler/src/mappers/letter-mapper.ts
+++ b/lambdas/api-handler/src/mappers/letter-mapper.ts
@@ -1,4 +1,4 @@
-import { LetterBase, LetterStatus, UpdateLetter } from "@internal/datastore";
+import { LetterBase, LetterStatus } from "@internal/datastore";
 import {
   GetLetterResponse,
   GetLetterResponseSchema,
@@ -68,22 +68,6 @@ export function mapToUpdateCommands(
   }));
 }
 
-// ---------------------------------------------
-//  Map letter command to repository type
-// ---------------------------------------------
-
-export function mapToUpdateLetter(
-  updateLetter: UpdateLetterCommand,
-): UpdateLetter {
-  return {
-    id: updateLetter.id,
-    supplierId: updateLetter.supplierId,
-    status: updateLetter.status,
-    reasonCode: updateLetter.reasonCode,
-    reasonText: updateLetter.reasonText,
-  };
-}
-
 // ---------------------------------------------
 //  Map internal datastore letter to response
 // ---------------------------------------------
diff --git a/lambdas/letter-updates-transformer/src/__tests__/letter-updates-transformer.test.ts b/lambdas/letter-updates-transformer/src/__tests__/letter-updates-transformer.test.ts
index f00e62935..fd11de133 100644
--- a/lambdas/letter-updates-transformer/src/__tests__/letter-updates-transformer.test.ts
+++ b/lambdas/letter-updates-transformer/src/__tests__/letter-updates-transformer.test.ts
@@ -7,13 +7,12 @@ import {
   KinesisStreamRecordPayload,
 } from "aws-lambda";
 import { mockDeep } from "jest-mock-extended";
-import { LetterBase } from "@internal/datastore";
+import { Letter } from "@internal/datastore";
+import { mapLetterToCloudEvent } from "@nhsdigital/nhs-notify-event-schemas-supplier-api/src/events/letter-mapper";
 import createHandler from "../letter-updates-transformer";
 import { Deps } from "../deps";
 import { EnvVars } from "../env";
-import mapLetterToCloudEvent from "../mappers/letter-mapper";
 import { LetterStatus } from "../../../api-handler/src/contracts/letters";
-import { LetterForEventPub } from "../types";
 
 // Make crypto return consistent values, since we"re calling it in both prod and test code and comparing the values
 const realCrypto = jest.requireActual("crypto");
@@ -171,7 +170,7 @@ describe("letter-updates-transformer Lambda", () => {
     it("does not publish invalid letter data", async () => {
       const handler = createHandler(mockedDeps);
       const oldLetter = generateLetter("ACCEPTED");
-      const newLetter = { id: oldLetter.id } as LetterForEventPub;
+      const newLetter = { id: oldLetter.id } as Letter;
 
       const testData = generateKinesisEvent([
         generateModifyRecord(oldLetter, newLetter),
@@ -324,7 +323,7 @@ describe("letter-updates-transformer Lambda", () => {
   });
 });
 
-function generateLetter(status: LetterStatus, id?: string): LetterForEventPub {
+function generateLetter(status: LetterStatus, id?: string): Letter {
   return {
     id: id || "1",
     status,
@@ -337,14 +336,14 @@ function generateLetter(status: LetterStatus, id?: string): LetterForEventPub {
     url: "https://example.com/letter.pdf",
     source: "test-source",
     subject: "test-source/subject-id",
+    supplierStatus: `supplier1#${status}`,
+    supplierStatusSk: "2025-12-10T11:12:54Z#1",
+    ttl: 1_234_567_890,
   };
 }
 
-function generateLetters(
-  numLetters: number,
-  status: LetterStatus,
-): LetterForEventPub[] {
-  const letters: LetterForEventPub[] = Array.from({ length: numLetters });
+function generateLetters(numLetters: number, status: LetterStatus): Letter[] {
+  const letters: Letter[] = Array.from({ length: numLetters });
   for (let i = 0; i < numLetters; i++) {
     letters[i] = generateLetter(status, String(i + 1));
   }
@@ -352,31 +351,34 @@ function generateLetters(
 }
 
 function generateModifyRecord(
-  oldLetter: LetterForEventPub,
-  newLetter: LetterForEventPub,
+  oldLetter: Letter,
+  newLetter: Letter,
 ): DynamoDBRecord {
-  const oldImage = Object.fromEntries(
-    Object.entries(oldLetter).map(([key, value]) => [key, { S: value }]),
-  );
-  const newImage = Object.fromEntries(
-    Object.entries(newLetter).map(([key, value]) => [key, { S: value }]),
-  );
+  const oldImage = buildStreamImage(oldLetter);
+  const newImage = buildStreamImage(newLetter);
   return {
     eventName: "MODIFY",
     dynamodb: { OldImage: oldImage, NewImage: newImage },
   };
 }
 
-function generateInsertRecord(newLetter: LetterBase): DynamoDBRecord {
-  const newImage = Object.fromEntries(
-    Object.entries(newLetter).map(([key, value]) => [key, { S: value }]),
-  );
+function generateInsertRecord(newLetter: Letter): DynamoDBRecord {
+  const newImage = buildStreamImage(newLetter);
   return {
     eventName: "INSERT",
     dynamodb: { NewImage: newImage },
   };
 }
 
+function buildStreamImage(letter: Letter) {
+  return Object.fromEntries(
+    Object.entries(letter).map(([key, value]) => [
+      key,
+      typeof value === "number" ? { N: String(value) } : { S: value },
+    ]),
+  );
+}
+
 function generateKinesisEvent(letterEvents: object[]): KinesisStreamEvent {
   const records = letterEvents
     .map((letter) => Buffer.from(JSON.stringify(letter)).toString("base64"))
diff --git a/lambdas/letter-updates-transformer/src/letter-updates-transformer.ts b/lambdas/letter-updates-transformer/src/letter-updates-transformer.ts
index 11b83c3b9..8ba2e1dd3 100644
--- a/lambdas/letter-updates-transformer/src/letter-updates-transformer.ts
+++ b/lambdas/letter-updates-transformer/src/letter-updates-transformer.ts
@@ -10,10 +10,10 @@ import {
   PublishBatchRequestEntry,
 } from "@aws-sdk/client-sns";
 import { LetterEvent } from "@nhsdigital/nhs-notify-event-schemas-supplier-api/src";
+import { mapLetterToCloudEvent } from "@nhsdigital/nhs-notify-event-schemas-supplier-api/src/events/letter-mapper";
+import { Letter, LetterSchema } from "@internal/datastore";
 import { MetricsLogger, Unit, metricScope } from "aws-embedded-metrics";
-import mapLetterToCloudEvent from "./mappers/letter-mapper";
 import { Deps } from "./deps";
-import { LetterForEventPub, LetterSchemaForEventPub } from "./types";
 
 // SNS PublishBatchCommand supports up to 10 messages per batch
 const BATCH_SIZE = 10;
@@ -140,9 +140,9 @@ function isChanged(record: DynamoDBRecord, property: string): boolean {
   return oldValue?.S !== newValue?.S;
 }
 
-function extractNewLetter(record: DynamoDBRecord): LetterForEventPub {
+function extractNewLetter(record: DynamoDBRecord): Letter {
   const newImage = record.dynamodb?.NewImage!;
-  return LetterSchemaForEventPub.parse(unmarshall(newImage as any));
+  return LetterSchema.parse(unmarshall(newImage as any));
 }
 
 function* generateBatches(events: LetterEvent[]) {
diff --git a/lambdas/letter-updates-transformer/src/types.ts b/lambdas/letter-updates-transformer/src/types.ts
deleted file mode 100644
index 34920991b..000000000
--- a/lambdas/letter-updates-transformer/src/types.ts
+++ /dev/null
@@ -1,10 +0,0 @@
-import { LetterSchema } from "@internal/datastore";
-import { z } from "zod";
-
-export const LetterSchemaForEventPub = LetterSchema.omit({
-  supplierStatus: true,
-  supplierStatusSk: true,
-  ttl: true,
-});
-
-export type LetterForEventPub = z.infer<typeof LetterSchemaForEventPub>;
diff --git a/lambdas/letter-updates-transformer/tsconfig.json b/lambdas/letter-updates-transformer/tsconfig.json
index f3fa0970e..bb8177b74 100644
--- a/lambdas/letter-updates-transformer/tsconfig.json
+++ b/lambdas/letter-updates-transformer/tsconfig.json
@@ -1,7 +1,6 @@
 {
   "compilerOptions": {
-    "esModuleInterop": true,
-    "resolveJsonModule": true
+    "esModuleInterop": true
   },
   "extends": "../../tsconfig.base.json",
   "include": [
diff --git a/lambdas/mi-updates-transformer/tsconfig.json b/lambdas/mi-updates-transformer/tsconfig.json
index f3fa0970e..bb8177b74 100644
--- a/lambdas/mi-updates-transformer/tsconfig.json
+++ b/lambdas/mi-updates-transformer/tsconfig.json
@@ -1,7 +1,6 @@
 {
   "compilerOptions": {
-    "esModuleInterop": true,
-    "resolveJsonModule": true
+    "esModuleInterop": true
   },
   "extends": "../../tsconfig.base.json",
   "include": [
diff --git a/lambdas/upsert-letter/src/handler/__tests__/upsert-handler.test.ts b/lambdas/upsert-letter/src/handler/__tests__/upsert-handler.test.ts
index 73826cd53..a94942d06 100644
--- a/lambdas/upsert-letter/src/handler/__tests__/upsert-handler.test.ts
+++ b/lambdas/upsert-letter/src/handler/__tests__/upsert-handler.test.ts
@@ -237,6 +237,7 @@ describe("createUpsertLetterHandler", () => {
     const firstArg = (mockedDeps.letterRepo.putLetter as jest.Mock).mock
       .calls[0][0];
     expect(firstArg.id).toBe("letter1");
+    expect(firstArg.eventId).toBe("7b9a03ca-342a-4150-b56b-989109c45613");
     expect(firstArg.supplierId).toBe("supplier1");
     expect(firstArg.specificationId).toBe("spec1");
     expect(firstArg.url).toBe("s3://letterDataBucket/letter1.pdf");
diff --git a/lambdas/upsert-letter/src/handler/upsert-handler.ts b/lambdas/upsert-letter/src/handler/upsert-handler.ts
index 49232369b..67893ff22 100644
--- a/lambdas/upsert-letter/src/handler/upsert-handler.ts
+++ b/lambdas/upsert-letter/src/handler/upsert-handler.ts
@@ -89,6 +89,7 @@ function mapToInsertLetter(
   const now = new Date().toISOString();
   return {
     id: upsertRequest.data.domainId,
+    eventId: upsertRequest.id,
     supplierId: supplier,
     status: "PENDING",
     specificationId: spec,
@@ -108,6 +109,7 @@ function mapToInsertLetter(
 function mapToUpdateLetter(upsertRequest: LetterEvent): UpdateLetter {
   return {
     id: upsertRequest.data.domainId,
+    eventId: upsertRequest.id,
     supplierId: upsertRequest.data.supplierId,
     status: upsertRequest.data.status,
     reasonCode: upsertRequest.data.reasonCode,
diff --git a/package-lock.json b/package-lock.json
index a63b758e2..d33bae5f3 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -148,6 +148,7 @@
       "license": "MIT",
       "dependencies": {
         "@asyncapi/bundler": "^0.6.4",
+        "@internal/datastore": "*",
         "zod": "^4.1.11"
       },
       "devDependencies": {
@@ -251,13 +252,15 @@
       "dependencies": {
         "@aws-sdk/client-dynamodb": "^3.984.0",
         "@aws-sdk/client-s3": "^3.925.0",
+        "@aws-sdk/client-sns": "^3.925.0",
         "@aws-sdk/client-sqs": "^3.925.0",
         "@aws-sdk/lib-dynamodb": "^3.925.0",
         "@aws-sdk/s3-request-presigner": "^3.925.0",
         "@internal/datastore": "*",
         "@internal/helpers": "*",
+        "@nhsdigital/nhs-notify-event-schemas-supplier-api": "*",
         "aws-embedded-metrics": "^4.2.1",
-        "aws-lambda": "^1.0.6",
+        "aws-lambda": "^1.0.7",
         "esbuild": "0.27.2",
         "pino": "^10.3.0",
         "zod": "^4.1.11"
@@ -275,6 +278,8 @@
     },
     "lambdas/api-handler/node_modules/argparse": {
       "version": "1.0.10",
+      "resolved": "https://registry.npmjs.org/argparse/-/argparse-1.0.10.tgz",
+      "integrity": "sha512-o5Roy6tNG4SL/FOkCAN6RzjiakZS25RLYFrcMttJqbdd8BWrnA+fGz57iN5Pb06pvBGvl5gQ0B48dJlslXvoTg==",
       "license": "MIT",
       "dependencies": {
         "sprintf-js": "~1.0.2"
@@ -282,6 +287,8 @@
     },
     "lambdas/api-handler/node_modules/aws-lambda": {
       "version": "1.0.7",
+      "resolved": "https://registry.npmjs.org/aws-lambda/-/aws-lambda-1.0.7.tgz",
+      "integrity": "sha512-9GNFMRrEMG5y3Jvv+V4azWvc+qNWdWLTjDdhf/zgMlz8haaaLWv0xeAIWxz9PuWUBawsVxy0zZotjCdR3Xq+2w==",
       "license": "MIT",
       "dependencies": {
         "aws-sdk": "^2.814.0",
@@ -295,10 +302,14 @@
     },
     "lambdas/api-handler/node_modules/commander": {
       "version": "3.0.2",
+      "resolved": "https://registry.npmjs.org/commander/-/commander-3.0.2.tgz",
+      "integrity": "sha512-Gar0ASD4BDyKC4hl4DwHqDrmvjoxWKZigVnAbn5H1owvm4CxCPdb0HQDehwNYMJpla5+M2tPmPARzhtYuwpHow==",
       "license": "MIT"
     },
     "lambdas/api-handler/node_modules/js-yaml": {
       "version": "3.14.2",
+      "resolved": "https://registry.npmjs.org/js-yaml/-/js-yaml-3.14.2.tgz",
+      "integrity": "sha512-PMSmkqxr106Xa156c2M265Z+FTrPl+oxd/rgOQy2tijQeK5TxQ43psO1ZCwhVOSdnn+RzkzlRz/eY4BgJBYVpg==",
       "license": "MIT",
       "dependencies": {
         "argparse": "^1.0.7",
diff --git a/package.json b/package.json
index ca391b99d..ee994074a 100644
--- a/package.json
+++ b/package.json
@@ -54,6 +54,7 @@
   "overrides": {
     "axios": "^1.13.5",
     "fast-xml-parser": "^5.3.4",
+    "@isaacs/brace-expansion": "^5.0.1",
     "pretty-format": {
       "react-is": "19.0.0"
     },
diff --git a/tsconfig.base.json b/tsconfig.base.json
index b340a8fa2..a0f424750 100644
--- a/tsconfig.base.json
+++ b/tsconfig.base.json
@@ -7,6 +7,7 @@
     "module": "ES2020",
     "moduleResolution": "node",
     "noEmit": true,
+    "resolveJsonModule": true,
     "skipLibCheck": true,
     "strict": true,
     "target": "ES2022"