diff --git a/infrastructure/terraform/components/api/module_authorizer_lambda.tf b/infrastructure/terraform/components/api/module_authorizer_lambda.tf
index 9a9b98acc..7fade5bae 100644
--- a/infrastructure/terraform/components/api/module_authorizer_lambda.tf
+++ b/infrastructure/terraform/components/api/module_authorizer_lambda.tf
@@ -39,6 +39,7 @@ module "authorizer_lambda" {
     CLIENT_CERTIFICATE_EXPIRATION_ALERT_DAYS = 30,
     APIM_SUPPLIER_ID_HEADER                  = "NHSD-Supplier-ID",
     SUPPLIERS_TABLE_NAME                     = aws_dynamodb_table.suppliers.name
+    LOG_REFERENCE                            = AUTHORIZER
   }
 }
 
diff --git a/infrastructure/terraform/components/api/module_lambda_amendment_event_transformer.tf b/infrastructure/terraform/components/api/module_lambda_amendment_event_transformer.tf
index 3cd0d5de2..0714bbc83 100644
--- a/infrastructure/terraform/components/api/module_lambda_amendment_event_transformer.tf
+++ b/infrastructure/terraform/components/api/module_lambda_amendment_event_transformer.tf
@@ -34,7 +34,9 @@ module "amendment_event_transformer" {
   log_destination_arn       = local.destination_arn
   log_subscription_role_arn = local.acct.log_subscription_role_arn
 
-  lambda_env_vars = merge(local.common_lambda_env_vars, {})
+  lambda_env_vars = merge(local.common_lambda_env_vars, {
+    LOG_REFERENCE = AMENDMENT_EVENT_TRANSFORMER
+  })
 }
 
 data "aws_iam_policy_document" "amendment_event_transformer" {
diff --git a/infrastructure/terraform/components/api/module_lambda_get_letter.tf b/infrastructure/terraform/components/api/module_lambda_get_letter.tf
index 845266816..7781cfc7a 100644
--- a/infrastructure/terraform/components/api/module_lambda_get_letter.tf
+++ b/infrastructure/terraform/components/api/module_lambda_get_letter.tf
@@ -34,7 +34,9 @@ module "get_letter" {
   log_destination_arn       = local.destination_arn
   log_subscription_role_arn = local.acct.log_subscription_role_arn
 
-  lambda_env_vars = merge(local.common_lambda_env_vars, {})
+  lambda_env_vars = merge(local.common_lambda_env_vars, {
+    LOG_REFERENCE = GET_LETTER
+  })
 }
 
 data "aws_iam_policy_document" "get_letter_lambda" {
diff --git a/infrastructure/terraform/components/api/module_lambda_get_letter_data.tf b/infrastructure/terraform/components/api/module_lambda_get_letter_data.tf
index 1129c6040..5c5a8d9db 100644
--- a/infrastructure/terraform/components/api/module_lambda_get_letter_data.tf
+++ b/infrastructure/terraform/components/api/module_lambda_get_letter_data.tf
@@ -34,7 +34,9 @@ module "get_letter_data" {
   log_destination_arn       = local.destination_arn
   log_subscription_role_arn = local.acct.log_subscription_role_arn
 
-  lambda_env_vars = merge(local.common_lambda_env_vars, {})
+  lambda_env_vars = merge(local.common_lambda_env_vars, {
+    LOG_REFERENCE = GET_LETTER_DATA
+  })
 }
 
 data "aws_iam_policy_document" "get_letter_data_lambda" {
diff --git a/infrastructure/terraform/components/api/module_lambda_get_letters.tf b/infrastructure/terraform/components/api/module_lambda_get_letters.tf
index 8c8482136..3349c38e2 100644
--- a/infrastructure/terraform/components/api/module_lambda_get_letters.tf
+++ b/infrastructure/terraform/components/api/module_lambda_get_letters.tf
@@ -35,7 +35,8 @@ module "get_letters" {
   log_subscription_role_arn = local.acct.log_subscription_role_arn
 
   lambda_env_vars = merge(local.common_lambda_env_vars, {
-    MAX_LIMIT = var.max_get_limit
+    MAX_LIMIT     = var.max_get_limit
+    LOG_REFERENCE = GET_LETTERS
   })
 }
 
diff --git a/infrastructure/terraform/components/api/module_lambda_get_mi.tf b/infrastructure/terraform/components/api/module_lambda_get_mi.tf
index 456bd588f..df38c02d5 100644
--- a/infrastructure/terraform/components/api/module_lambda_get_mi.tf
+++ b/infrastructure/terraform/components/api/module_lambda_get_mi.tf
@@ -34,7 +34,8 @@ module "get_mi" {
   log_destination_arn       = local.destination_arn
   log_subscription_role_arn = local.acct.log_subscription_role_arn
 
-  lambda_env_vars = merge(local.common_lambda_env_vars, {})
+  lambda_env_vars = merge(local.common_lambda_env_vars, {
+  LOG_REFERENCE = GET_MI })
 }
 
 data "aws_iam_policy_document" "get_mi_lambda" {
diff --git a/infrastructure/terraform/components/api/module_lambda_get_status.tf b/infrastructure/terraform/components/api/module_lambda_get_status.tf
index 7582de805..6cd82379b 100644
--- a/infrastructure/terraform/components/api/module_lambda_get_status.tf
+++ b/infrastructure/terraform/components/api/module_lambda_get_status.tf
@@ -34,7 +34,9 @@ module "get_status" {
   log_destination_arn       = local.destination_arn
   log_subscription_role_arn = local.acct.log_subscription_role_arn
 
-  lambda_env_vars = merge(local.common_lambda_env_vars, {})
+  lambda_env_vars = merge(local.common_lambda_env_vars, {
+    LOG_REFERENCE = GET_STATUS
+  })
 }
 
 data "aws_iam_policy_document" "get_status_lambda" {
diff --git a/infrastructure/terraform/components/api/module_lambda_letter_updates_transformer.tf b/infrastructure/terraform/components/api/module_lambda_letter_updates_transformer.tf
index 20a117f50..060fd2a19 100644
--- a/infrastructure/terraform/components/api/module_lambda_letter_updates_transformer.tf
+++ b/infrastructure/terraform/components/api/module_lambda_letter_updates_transformer.tf
@@ -37,6 +37,7 @@ module "letter_updates_transformer" {
   lambda_env_vars = merge(local.common_lambda_env_vars, {
     EVENTPUB_SNS_TOPIC_ARN = "${module.eventpub.sns_topic.arn}",
     EVENT_SOURCE           = var.letter_event_source
+    LOG_REFERENCE          = LETTER_UPDATES_TRANSFORMER
   })
 }
 
diff --git a/infrastructure/terraform/components/api/module_lambda_mi_updates_transformer.tf b/infrastructure/terraform/components/api/module_lambda_mi_updates_transformer.tf
index 47bdbbfe0..4c10c76d8 100644
--- a/infrastructure/terraform/components/api/module_lambda_mi_updates_transformer.tf
+++ b/infrastructure/terraform/components/api/module_lambda_mi_updates_transformer.tf
@@ -37,6 +37,7 @@ module "mi_updates_transformer" {
 
   lambda_env_vars = merge(local.common_lambda_env_vars, {
     EVENTPUB_SNS_TOPIC_ARN = "${module.eventpub.sns_topic.arn}"
+    LOG_REFERENCE          = MI_UPDATES_TRANSFORMER
   })
 }
 
diff --git a/infrastructure/terraform/components/api/module_lambda_patch_letter.tf b/infrastructure/terraform/components/api/module_lambda_patch_letter.tf
index afc612c71..f8516ac23 100644
--- a/infrastructure/terraform/components/api/module_lambda_patch_letter.tf
+++ b/infrastructure/terraform/components/api/module_lambda_patch_letter.tf
@@ -35,7 +35,8 @@ 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.amendments_queue.sqs_queue_url
+    QUEUE_URL     = module.amendments_queue.sqs_queue_url
+    LOG_REFERENCE = PATCH_LETTERS
   })
 }
 
diff --git a/infrastructure/terraform/components/api/module_lambda_post_letters.tf b/infrastructure/terraform/components/api/module_lambda_post_letters.tf
index 272f4c9e9..7b9d8e61c 100644
--- a/infrastructure/terraform/components/api/module_lambda_post_letters.tf
+++ b/infrastructure/terraform/components/api/module_lambda_post_letters.tf
@@ -35,8 +35,9 @@ 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.amendments_queue.sqs_queue_url,
-    MAX_LIMIT = var.max_get_limit
+    QUEUE_URL     = module.amendments_queue.sqs_queue_url,
+    MAX_LIMIT     = var.max_get_limit
+    LOG_REFERENCE = POST_LETTERS
   })
 }
 
diff --git a/infrastructure/terraform/components/api/module_lambda_post_mi.tf b/infrastructure/terraform/components/api/module_lambda_post_mi.tf
index be7ae4eed..f1152fbc9 100644
--- a/infrastructure/terraform/components/api/module_lambda_post_mi.tf
+++ b/infrastructure/terraform/components/api/module_lambda_post_mi.tf
@@ -34,7 +34,9 @@ module "post_mi" {
   log_destination_arn       = local.destination_arn
   log_subscription_role_arn = local.acct.log_subscription_role_arn
 
-  lambda_env_vars = merge(local.common_lambda_env_vars, {})
+  lambda_env_vars = merge(local.common_lambda_env_vars, {
+    LOG_REFERENCE = POST_MI
+  })
 }
 
 data "aws_iam_policy_document" "post_mi_lambda" {
diff --git a/infrastructure/terraform/components/api/module_lambda_supplier_allocator.tf b/infrastructure/terraform/components/api/module_lambda_supplier_allocator.tf
index b0354bd88..7ae1906cd 100644
--- a/infrastructure/terraform/components/api/module_lambda_supplier_allocator.tf
+++ b/infrastructure/terraform/components/api/module_lambda_supplier_allocator.tf
@@ -37,6 +37,7 @@ module "supplier_allocator" {
   lambda_env_vars = merge(local.common_lambda_env_vars, {
     UPSERT_LETTERS_QUEUE_URL = module.sqs_letter_updates.sqs_queue_url,
     IDEMPOTENCY_TABLE_NAME   = aws_dynamodb_table.idempotency.name
+    LOG_REFERENCE            = SUPPLIER_ALLOCATOR
   })
 }
 
diff --git a/infrastructure/terraform/components/api/module_lambda_supplier_config_ingress.tf b/infrastructure/terraform/components/api/module_lambda_supplier_config_ingress.tf
index 8073ffef6..568afc506 100644
--- a/infrastructure/terraform/components/api/module_lambda_supplier_config_ingress.tf
+++ b/infrastructure/terraform/components/api/module_lambda_supplier_config_ingress.tf
@@ -34,7 +34,9 @@ module "supplier_config_ingress" {
   log_destination_arn       = local.destination_arn
   log_subscription_role_arn = local.acct.log_subscription_role_arn
 
-  lambda_env_vars = merge(local.common_lambda_env_vars, {})
+  lambda_env_vars = merge(local.common_lambda_env_vars, {
+    LOG_REFERENCE = SUPPLIER_CONFIG_INGRESS
+  })
 }
 
 data "aws_iam_policy_document" "supplier_config_ingress_lambda" {
diff --git a/infrastructure/terraform/components/api/module_lambda_supplier_mock.tf b/infrastructure/terraform/components/api/module_lambda_supplier_mock.tf
index eb17faf34..649f1a565 100644
--- a/infrastructure/terraform/components/api/module_lambda_supplier_mock.tf
+++ b/infrastructure/terraform/components/api/module_lambda_supplier_mock.tf
@@ -40,6 +40,7 @@ module "supplier_mock" {
     GET_LETTERS_FUNCTION_NAME       = module.get_letters.function_name
     PATCH_LETTER_FUNCTION_NAME      = module.patch_letter.function_name
     SUPPLIER_MOCK_CONFIG_PARAM_NAME = aws_ssm_parameter.supplier_mock_config[0].name
+    LOG_REFERENCE                   = SUPPLIER_MOCK
   })
 }
 
diff --git a/infrastructure/terraform/components/api/module_lambda_update_letter_queue.tf b/infrastructure/terraform/components/api/module_lambda_update_letter_queue.tf
index 418bd216a..b8dcb63d3 100644
--- a/infrastructure/terraform/components/api/module_lambda_update_letter_queue.tf
+++ b/infrastructure/terraform/components/api/module_lambda_update_letter_queue.tf
@@ -34,7 +34,9 @@ module "update_letter_queue" {
   log_destination_arn       = local.destination_arn
   log_subscription_role_arn = local.acct.log_subscription_role_arn
 
-  lambda_env_vars = merge(local.common_lambda_env_vars, {})
+  lambda_env_vars = merge(local.common_lambda_env_vars, {
+    LOG_REFERENCE = UPDATE_LETTER
+  })
 }
 
 data "aws_iam_policy_document" "update_letter_queue_lambda" {
diff --git a/infrastructure/terraform/components/api/module_lambda_upsert_letter.tf b/infrastructure/terraform/components/api/module_lambda_upsert_letter.tf
index eeaed3420..1b99bdd40 100644
--- a/infrastructure/terraform/components/api/module_lambda_upsert_letter.tf
+++ b/infrastructure/terraform/components/api/module_lambda_upsert_letter.tf
@@ -36,6 +36,7 @@ module "upsert_letter" {
 
   lambda_env_vars = merge(local.common_lambda_env_vars, {
     IDEMPOTENCY_TABLE_NAME = aws_dynamodb_table.idempotency.name
+    LOG_REFERENCE          = UPSERT_LETTER
   })
 }
 
diff --git a/internal/helpers/src/logger.ts b/internal/helpers/src/logger.ts
index 051e793be..1a7144522 100644
--- a/internal/helpers/src/logger.ts
+++ b/internal/helpers/src/logger.ts
@@ -2,6 +2,7 @@ import pino, { Logger } from "pino";
 
 export type LoggerOptions = {
   logLevel?: string;
+  logReference?: string;
 };
 
 /**
@@ -9,13 +10,17 @@ export type LoggerOptions = {
  *
  * @param options - Optional configuration for the logger
  * @param options.logLevel - The log level (defaults to "info")
+ * @param options.logReference - Optional reference value to include on every log record
  * @returns A configured pino Logger instance
  */
 export function createLogger(options: LoggerOptions = {}): Logger {
-  const { logLevel = "info" } = options;
+  const { logLevel = "info", logReference } = options;
 
   return pino({
     level: logLevel,
+    mixin: () => {
+      return logReference ? { log_reference: logReference } : {};
+    },
     formatters: {
       level: (label) => {
         return { level: label.toUpperCase() };
diff --git a/lambdas/api-handler/src/config/deps.ts b/lambdas/api-handler/src/config/deps.ts
index 427d883fa..610a43cc1 100644
--- a/lambdas/api-handler/src/config/deps.ts
+++ b/lambdas/api-handler/src/config/deps.ts
@@ -73,7 +73,10 @@ function createMIRepository(log: Logger, environment: EnvVars): MIRepository {
 }
 
 export function createDependenciesContainer(): Deps {
-  const log = createLogger({ logLevel: envVars.PINO_LOG_LEVEL });
+  const log = createLogger({
+    logLevel: envVars.PINO_LOG_LEVEL,
+    logReference: envVars.LOG_REFERENCE,
+  });
 
   return {
     s3Client: new S3Client(),
diff --git a/lambdas/api-handler/src/config/env.ts b/lambdas/api-handler/src/config/env.ts
index a7402eee6..da32e2fa8 100644
--- a/lambdas/api-handler/src/config/env.ts
+++ b/lambdas/api-handler/src/config/env.ts
@@ -16,6 +16,7 @@ const EnvVarsSchema = z.object({
   PINO_LOG_LEVEL: z.coerce.string().optional(),
   EVENT_SOURCE: z.string(),
   SNS_TOPIC_ARN: z.string(),
+  LOG_REFERENCE: z.string().optional(),
 });
 
 export type EnvVars = z.infer<typeof EnvVarsSchema>;
diff --git a/lambdas/authorizer/src/deps.ts b/lambdas/authorizer/src/deps.ts
index 6ea7ee079..445b4f2d0 100644
--- a/lambdas/authorizer/src/deps.ts
+++ b/lambdas/authorizer/src/deps.ts
@@ -29,7 +29,10 @@ function createSupplierRepository(
 }
 
 export function createDependenciesContainer(): Deps {
-  const log = createLogger({ logLevel: envVars.PINO_LOG_LEVEL });
+  const log = createLogger({
+    logLevel: envVars.PINO_LOG_LEVEL,
+    logReference: envVars.LOG_REFERENCE,
+  });
 
   return {
     supplierRepo: createSupplierRepository(
diff --git a/lambdas/authorizer/src/env.ts b/lambdas/authorizer/src/env.ts
index a81f82f2d..2196d64bc 100644
--- a/lambdas/authorizer/src/env.ts
+++ b/lambdas/authorizer/src/env.ts
@@ -6,6 +6,7 @@ const EnvVarsSchema = z.object({
   APIM_SUPPLIER_ID_HEADER: z.string(),
   CLIENT_CERTIFICATE_EXPIRATION_ALERT_DAYS: z.coerce.number().int(),
   PINO_LOG_LEVEL: z.coerce.string().optional(),
+  LOG_REFERENCE: z.string().optional(),
 });
 
 export type EnvVars = z.infer<typeof EnvVarsSchema>;
diff --git a/lambdas/letter-updates-transformer/src/deps.ts b/lambdas/letter-updates-transformer/src/deps.ts
index 57831c7a3..79d0d8425 100644
--- a/lambdas/letter-updates-transformer/src/deps.ts
+++ b/lambdas/letter-updates-transformer/src/deps.ts
@@ -14,7 +14,10 @@ function createSNSClient(): SNSClient {
 }
 
 export function createDependenciesContainer(): Deps {
-  const log = createLogger({ logLevel: envVars.PINO_LOG_LEVEL });
+  const log = createLogger({
+    logLevel: envVars.PINO_LOG_LEVEL,
+    logReference: envVars.LOG_REFERENCE,
+  });
 
   return {
     snsClient: createSNSClient(),
diff --git a/lambdas/letter-updates-transformer/src/env.ts b/lambdas/letter-updates-transformer/src/env.ts
index 33030ad8b..72a04f0ce 100644
--- a/lambdas/letter-updates-transformer/src/env.ts
+++ b/lambdas/letter-updates-transformer/src/env.ts
@@ -4,6 +4,7 @@ const EnvVarsSchema = z.object({
   EVENTPUB_SNS_TOPIC_ARN: z.string(),
   EVENT_SOURCE: z.string(),
   PINO_LOG_LEVEL: z.coerce.string().optional(),
+  LOG_REFERENCE: z.string().optional(),
 });
 
 export type EnvVars = z.infer<typeof EnvVarsSchema>;
diff --git a/lambdas/mi-updates-transformer/src/deps.ts b/lambdas/mi-updates-transformer/src/deps.ts
index 57831c7a3..79d0d8425 100644
--- a/lambdas/mi-updates-transformer/src/deps.ts
+++ b/lambdas/mi-updates-transformer/src/deps.ts
@@ -14,7 +14,10 @@ function createSNSClient(): SNSClient {
 }
 
 export function createDependenciesContainer(): Deps {
-  const log = createLogger({ logLevel: envVars.PINO_LOG_LEVEL });
+  const log = createLogger({
+    logLevel: envVars.PINO_LOG_LEVEL,
+    logReference: envVars.LOG_REFERENCE,
+  });
 
   return {
     snsClient: createSNSClient(),
diff --git a/lambdas/mi-updates-transformer/src/env.ts b/lambdas/mi-updates-transformer/src/env.ts
index fb4fe6089..fb5d51ee8 100644
--- a/lambdas/mi-updates-transformer/src/env.ts
+++ b/lambdas/mi-updates-transformer/src/env.ts
@@ -3,6 +3,7 @@ import { z } from "zod";
 const EnvVarsSchema = z.object({
   EVENTPUB_SNS_TOPIC_ARN: z.string(),
   PINO_LOG_LEVEL: z.coerce.string().optional(),
+  LOG_REFERENCE: z.string().optional(),
 });
 
 export type EnvVars = z.infer<typeof EnvVarsSchema>;
diff --git a/lambdas/supplier-allocator/src/config/deps.ts b/lambdas/supplier-allocator/src/config/deps.ts
index e937d64ef..75b31fa4e 100644
--- a/lambdas/supplier-allocator/src/config/deps.ts
+++ b/lambdas/supplier-allocator/src/config/deps.ts
@@ -47,7 +47,10 @@ function createIdempotencyLayer(): DynamoDBPersistenceLayer {
 }
 
 export function createDependenciesContainer(): Deps {
-  const log = createLogger({ logLevel: envVars.PINO_LOG_LEVEL });
+  const log = createLogger({
+    logLevel: envVars.PINO_LOG_LEVEL,
+    logReference: envVars.LOG_REFERENCE,
+  });
 
   return {
     supplierConfigRepo: createSupplierConfigRepository(),
diff --git a/lambdas/supplier-allocator/src/config/env.ts b/lambdas/supplier-allocator/src/config/env.ts
index 7d99ef0df..53eb22834 100644
--- a/lambdas/supplier-allocator/src/config/env.ts
+++ b/lambdas/supplier-allocator/src/config/env.ts
@@ -5,6 +5,7 @@ const EnvVarsSchema = z.object({
   SUPPLIER_QUOTAS_TABLE_NAME: z.string(),
   PINO_LOG_LEVEL: z.coerce.string().optional(),
   IDEMPOTENCY_TABLE_NAME: z.string(),
+  LOG_REFERENCE: z.string().optional(),
 });
 
 export type EnvVars = z.infer<typeof EnvVarsSchema>;
diff --git a/lambdas/supplier-config-ingress/src/config/deps.ts b/lambdas/supplier-config-ingress/src/config/deps.ts
index ec8ab9c6e..fc5c1dc91 100644
--- a/lambdas/supplier-config-ingress/src/config/deps.ts
+++ b/lambdas/supplier-config-ingress/src/config/deps.ts
@@ -28,7 +28,10 @@ function createSupplierConfigRepository(
 }
 
 export function createDependenciesContainer(): Deps {
-  const log = createLogger({ logLevel: envVars.PINO_LOG_LEVEL });
+  const log = createLogger({
+    logLevel: envVars.PINO_LOG_LEVEL,
+    logReference: envVars.LOG_REFERENCE,
+  });
 
   return {
     supplierConfigRepo: createSupplierConfigRepository(envVars),
diff --git a/lambdas/supplier-config-ingress/src/config/env.ts b/lambdas/supplier-config-ingress/src/config/env.ts
index e037d73d2..156dbb87a 100644
--- a/lambdas/supplier-config-ingress/src/config/env.ts
+++ b/lambdas/supplier-config-ingress/src/config/env.ts
@@ -3,6 +3,8 @@ import { z } from "zod";
 const EnvVarsSchema = z.object({
   SUPPLIER_CONFIG_TABLE_NAME: z.string(),
   PINO_LOG_LEVEL: z.coerce.string().optional(),
+  IDEMPOTENCY_TABLE_NAME: z.string(),
+  LOG_REFERENCE: z.string().optional(),
 });
 
 export type EnvVars = z.infer<typeof EnvVarsSchema>;
diff --git a/lambdas/supplier-mock/src/handler/deps.ts b/lambdas/supplier-mock/src/handler/deps.ts
index 98775641e..45103e0fa 100644
--- a/lambdas/supplier-mock/src/handler/deps.ts
+++ b/lambdas/supplier-mock/src/handler/deps.ts
@@ -16,7 +16,11 @@ export type Deps = {
 };
 
 export function createDependenciesContainer(): Deps {
-  const log = createLogger({ logLevel: envVars.PINO_LOG_LEVEL });
+  const log = createLogger({
+    logLevel: envVars.PINO_LOG_LEVEL,
+    logReference: envVars.LOG_REFERENCE,
+  });
+
   const lambdaClient = new LambdaClient();
   const parameterStoreConfig = getParameterStoreConfig();
 
diff --git a/lambdas/supplier-mock/src/handler/env.ts b/lambdas/supplier-mock/src/handler/env.ts
index e076faac3..c957f0e22 100644
--- a/lambdas/supplier-mock/src/handler/env.ts
+++ b/lambdas/supplier-mock/src/handler/env.ts
@@ -7,6 +7,7 @@ const EnvVarsSchema = z.object({
   GET_LETTERS_FUNCTION_NAME: z.string().optional(),
   PATCH_LETTER_FUNCTION_NAME: z.string().optional(),
   SUPPLIER_MOCK_CONFIG_PARAM_NAME: z.string().optional(),
+  LOG_REFERENCE: z.string().optional(),
 });
 
 export type EnvVars = z.infer<typeof EnvVarsSchema>;
diff --git a/lambdas/update-letter-queue/src/deps.ts b/lambdas/update-letter-queue/src/deps.ts
index 9db089111..926e9f9bd 100644
--- a/lambdas/update-letter-queue/src/deps.ts
+++ b/lambdas/update-letter-queue/src/deps.ts
@@ -17,7 +17,10 @@ function createDynamoDBDocumentClient(): DynamoDBDocumentClient {
 }
 
 export function createDependenciesContainer(): Deps {
-  const log = createLogger({ logLevel: envVars.PINO_LOG_LEVEL });
+  const log = createLogger({
+    logLevel: envVars.PINO_LOG_LEVEL,
+    logReference: envVars.LOG_REFERENCE,
+  });
   const ddbClient = createDynamoDBDocumentClient();
 
   const letterQueueRepository = new LetterQueueRepository(ddbClient, log, {
diff --git a/lambdas/update-letter-queue/src/env.ts b/lambdas/update-letter-queue/src/env.ts
index d54353325..94836b5b7 100644
--- a/lambdas/update-letter-queue/src/env.ts
+++ b/lambdas/update-letter-queue/src/env.ts
@@ -4,6 +4,7 @@ const EnvVarsSchema = z.object({
   LETTER_QUEUE_TABLE_NAME: z.string(),
   LETTER_QUEUE_TTL_HOURS: z.coerce.number().int(),
   PINO_LOG_LEVEL: z.coerce.string().optional(),
+  LOG_REFERENCE: z.string().optional(),
 });
 
 export type EnvVars = z.infer<typeof EnvVarsSchema>;
diff --git a/lambdas/upsert-letter/src/config/deps.ts b/lambdas/upsert-letter/src/config/deps.ts
index 09292c6a3..4f2f1b871 100644
--- a/lambdas/upsert-letter/src/config/deps.ts
+++ b/lambdas/upsert-letter/src/config/deps.ts
@@ -34,7 +34,10 @@ function createIdempotencyLayer(): DynamoDBPersistenceLayer {
 }
 
 export function createDependenciesContainer(): Deps {
-  const log = createLogger({ logLevel: envVars.PINO_LOG_LEVEL });
+  const log = createLogger({
+    logLevel: envVars.PINO_LOG_LEVEL,
+    logReference: envVars.LOG_REFERENCE,
+  });
 
   return {
     letterRepo: createLetterRepository(log),
diff --git a/lambdas/upsert-letter/src/config/env.ts b/lambdas/upsert-letter/src/config/env.ts
index 1f3a3bdf8..f93d61a79 100644
--- a/lambdas/upsert-letter/src/config/env.ts
+++ b/lambdas/upsert-letter/src/config/env.ts
@@ -5,6 +5,7 @@ const EnvVarsSchema = z.object({
   LETTER_TTL_HOURS: z.coerce.number().int(),
   PINO_LOG_LEVEL: z.coerce.string().optional(),
   IDEMPOTENCY_TABLE_NAME: z.string(),
+  LOG_REFERENCE: z.string().optional(),
 });
 
 export type EnvVars = z.infer<typeof EnvVarsSchema>;