diff --git a/src/ServiceControl.Audit.Persistence.InMemory/InMemoryFailedAuditStorage.cs b/src/ServiceControl.Audit.Persistence.InMemory/InMemoryFailedAuditStorage.cs
index 652b79983e..e6dbf35e02 100644
--- a/src/ServiceControl.Audit.Persistence.InMemory/InMemoryFailedAuditStorage.cs
+++ b/src/ServiceControl.Audit.Persistence.InMemory/InMemoryFailedAuditStorage.cs
@@ -25,7 +25,15 @@ public async Task ProcessFailedMessages(Func<FailedTransportMessage, Func<Cancel
         public Task SaveFailedAuditImport(FailedAuditImport message, CancellationToken cancellationToken = default)
         {
             cancellationToken.ThrowIfCancellationRequested();
-            dataStore.failedAuditImports.Add(message);
+            var existing = message.Id == null ? -1 : dataStore.failedAuditImports.FindIndex(x => x.Id == message.Id);
+            if (existing >= 0)
+            {
+                dataStore.failedAuditImports[existing] = message;
+            }
+            else
+            {
+                dataStore.failedAuditImports.Add(message);
+            }
             return Task.CompletedTask;
         }
 
diff --git a/src/ServiceControl.Audit.Persistence.RavenDB/RavenFailedAuditStorage.cs b/src/ServiceControl.Audit.Persistence.RavenDB/RavenFailedAuditStorage.cs
index 183907a9ed..56573c3bb5 100644
--- a/src/ServiceControl.Audit.Persistence.RavenDB/RavenFailedAuditStorage.cs
+++ b/src/ServiceControl.Audit.Persistence.RavenDB/RavenFailedAuditStorage.cs
@@ -15,6 +15,10 @@ class RavenFailedAuditStorage(IRavenSessionProvider sessionProvider) : IFailedAu
         public async Task SaveFailedAuditImport(FailedAuditImport message, CancellationToken cancellationToken = default)
         {
             using var session = await sessionProvider.OpenSession(cancellationToken: cancellationToken);
+            if (message.Id != null && !message.Id.StartsWith("FailedAuditImports/", StringComparison.OrdinalIgnoreCase))
+            {
+                message.Id = $"FailedAuditImports/{message.Id}";
+            }
             await session.StoreAsync(message, token: cancellationToken);
             await session.SaveChangesAsync(cancellationToken);
         }
diff --git a/src/ServiceControl.Audit.Persistence.Tests/FailedAuditStorageTests.cs b/src/ServiceControl.Audit.Persistence.Tests/FailedAuditStorageTests.cs
index c450ff6e25..473fcf6e59 100644
--- a/src/ServiceControl.Audit.Persistence.Tests/FailedAuditStorageTests.cs
+++ b/src/ServiceControl.Audit.Persistence.Tests/FailedAuditStorageTests.cs
@@ -1,8 +1,10 @@
 namespace ServiceControl.Audit.Persistence.Tests
 {
     using System;
+    using System.Collections.Generic;
     using System.Threading;
     using System.Threading.Tasks;
+    using NServiceBus;
     using NUnit.Framework;
     using ServiceControl.Audit.Auditing;
 
@@ -21,6 +23,35 @@ public async Task Should_store_failures()
             Assert.That(numFailures, Is.EqualTo(1));
         }
 
+        [Test]
+        public async Task Repeated_failure_of_the_same_message_stores_one_document()
+        {
+            var headers = new Dictionary<string, string>
+            {
+                { Headers.MessageId, "message-1" },
+                { Headers.ProcessingEndpoint, "Sales" }
+            };
+            await FailedAuditStorage.SaveFailedAuditImport(new FailedAuditImport { Id = FailedAuditImport.DeriveKey(headers, "native-1").ToString() });
+            await FailedAuditStorage.SaveFailedAuditImport(new FailedAuditImport { Id = FailedAuditImport.DeriveKey(headers, "native-1").ToString() });
+            await configuration.CompleteDBOperation();
+
+            Assert.That(await FailedAuditStorage.GetFailedAuditsCount(), Is.EqualTo(1));
+        }
+
+        [Test]
+        public void DeriveKey_uses_retry_id_or_falls_back_for_malformed_headers()
+        {
+            var retryId = Guid.NewGuid();
+            var headers = new Dictionary<string, string> { ["ServiceControl.Retry.UniqueMessageId"] = retryId.ToString() };
+
+            var fallback = FailedAuditImport.DeriveKey(new Dictionary<string, string>(), "native-1");
+            Assert.That(FailedAuditImport.DeriveKey(headers, "native-1"), Is.EqualTo(retryId));
+            Assert.That(FailedAuditImport.DeriveKey(new Dictionary<string, string>(), "native-1"), Is.EqualTo(fallback));
+            Assert.That(FailedAuditImport.DeriveKey(new Dictionary<string, string>(), "native-2"), Is.Not.EqualTo(fallback));
+            headers["ServiceControl.Retry.UniqueMessageId"] = "not-a-guid";
+            Assert.That(FailedAuditImport.DeriveKey(headers, "native-1"), Is.EqualTo(fallback));
+        }
+
         [Test]
         public async Task Should_be_able_to_process_failures()
         {
diff --git a/src/ServiceControl.Audit.Persistence/FailedAuditImport.cs b/src/ServiceControl.Audit.Persistence/FailedAuditImport.cs
index da916151e3..bcf824281d 100644
--- a/src/ServiceControl.Audit.Persistence/FailedAuditImport.cs
+++ b/src/ServiceControl.Audit.Persistence/FailedAuditImport.cs
@@ -1,9 +1,30 @@
 namespace ServiceControl.Audit.Auditing
 {
+    using System;
+    using System.Collections.Generic;
+    using ServiceControl.Audit.Persistence.Infrastructure;
+
     public class FailedAuditImport
     {
         public string Id { get; set; }
         public FailedTransportMessage Message { get; set; }
         public string ExceptionInfo { get; set; }
+
+        public static Guid DeriveKey(IReadOnlyDictionary<string, string> headers, string nativeMessageId)
+        {
+            try
+            {
+                if (Guid.TryParse(headers.UniqueId(), out var uniqueMessageId))
+                {
+                    return uniqueMessageId;
+                }
+            }
+            catch (Exception)
+            {
+                // Malformed messages may have no processing endpoint; the transport ID is always available.
+            }
+
+            return DeterministicGuid.MakeId(nativeMessageId);
+        }
     }
 }
\ No newline at end of file
diff --git a/src/ServiceControl.Audit/Auditing/AuditIngestionFaultPolicy.cs b/src/ServiceControl.Audit/Auditing/AuditIngestionFaultPolicy.cs
index b9d323747f..54c1d6221d 100644
--- a/src/ServiceControl.Audit/Auditing/AuditIngestionFaultPolicy.cs
+++ b/src/ServiceControl.Audit/Auditing/AuditIngestionFaultPolicy.cs
@@ -56,7 +56,7 @@ async Task StoreFailedMessageDocument(ErrorContext errorContext, CancellationTok
     {
         var failure = new FailedAuditImport
         {
-            Id = Guid.NewGuid().ToString(),
+            Id = FailedAuditImport.DeriveKey(errorContext.Headers, errorContext.MessageId).ToString(),
             Message = new FailedTransportMessage
             {
                 Id = errorContext.MessageId,