diff --git a/include/hardware/bt_gatt_client.h b/include/hardware/bt_gatt_client.h
index d650671..d20c2e8 100644
--- a/include/hardware/bt_gatt_client.h
+++ b/include/hardware/bt_gatt_client.h
@@ -174,6 +174,13 @@
 /** Callback invoked when multi-adv disable operation has completed */
 typedef void (*multi_adv_disable_callback)(int client_if, int status);
 
+/**
+ * Callback notifying an application that a remote device connection is currently congested
+ * and cannot receive any more data. An application should avoid sending more data until
+ * a further callback is received indicating the congestion status has been cleared.
+ */
+typedef void (*congestion_callback)(int conn_id, bool congested);
+
 typedef struct {
     register_client_callback            register_client_cb;
     scan_result_callback                scan_result_cb;
@@ -199,6 +206,7 @@
     multi_adv_update_callback           multi_adv_update_cb;
     multi_adv_data_callback             multi_adv_data_cb;
     multi_adv_disable_callback          multi_adv_disable_cb;
+    congestion_callback                 congestion_cb;
 } btgatt_client_callbacks_t;
 
 /** Represents the standard BT-GATT client interface. */
diff --git a/include/hardware/bt_gatt_server.h b/include/hardware/bt_gatt_server.h
index 32f8ef6..2b1de27 100644
--- a/include/hardware/bt_gatt_server.h
+++ b/include/hardware/bt_gatt_server.h
@@ -104,6 +104,19 @@
  */
 typedef void (*response_confirmation_callback)(int status, int handle);
 
+/**
+ * Callback confirming that a notification or indication has been sent
+ * to a remote device.
+ */
+typedef void (*indication_sent_callback)(int conn_id, int status);
+
+/**
+ * Callback notifying an application that a remote device connection is currently congested
+ * and cannot receive any more data. An application should avoid sending more data until
+ * a further callback is received indicating the congestion status has been cleared.
+ */
+typedef void (*congestion_callback)(int conn_id, bool congested);
+
 typedef struct {
     register_server_callback        register_server_cb;
     connection_callback             connection_cb;
@@ -118,6 +131,8 @@
     request_write_callback          request_write_cb;
     request_exec_write_callback     request_exec_write_cb;
     response_confirmation_callback  response_confirmation_cb;
+    indication_sent_callback        indication_sent_cb;
+    congestion_callback             congestion_cb;
 } btgatt_server_callbacks_t;
 
 /** Represents the standard BT-GATT server interface. */