diff --git a/src/ScadaLink.Commons/Entities/Notifications/Notification.cs b/src/ScadaLink.Commons/Entities/Notifications/Notification.cs
new file mode 100644
index 0000000..ab94f56
--- /dev/null
+++ b/src/ScadaLink.Commons/Entities/Notifications/Notification.cs
@@ -0,0 +1,48 @@
+using ScadaLink.Commons.Types.Enums;
+
+namespace ScadaLink.Commons.Entities.Notifications;
+
+/// <summary>
+/// A single notification queued in the central outbox. Created at a site (where the
+/// <see cref="NotificationId"/> GUID is generated) and forwarded to the central cluster
+/// for delivery, retry, and audit. The lifecycle is tracked by <see cref="Status"/>.
+/// </summary>
+public class Notification
+{
+    /// <summary>GUID primary key, generated at the originating site.</summary>
+    public string NotificationId { get; set; }
+    public NotificationType Type { get; set; }
+    public string ListName { get; set; }
+    public string Subject { get; set; }
+    public string Body { get; set; }
+
+    /// <summary>JSON extensibility hook for channel-specific payload data.</summary>
+    public string? TypeData { get; set; }
+    public NotificationStatus Status { get; set; } = NotificationStatus.Pending;
+    public int RetryCount { get; set; }
+    public string? LastError { get; set; }
+
+    /// <summary>Resolved delivery targets snapshotted at delivery time, for audit.</summary>
+    public string? ResolvedTargets { get; set; }
+    public string SourceSiteId { get; set; }
+    public string? SourceInstanceId { get; set; }
+    public string? SourceScript { get; set; }
+    public DateTimeOffset SiteEnqueuedAt { get; set; }
+
+    /// <summary>Central ingest time.</summary>
+    public DateTimeOffset CreatedAt { get; set; }
+    public DateTimeOffset? LastAttemptAt { get; set; }
+    public DateTimeOffset? NextAttemptAt { get; set; }
+    public DateTimeOffset? DeliveredAt { get; set; }
+
+    public Notification(string notificationId, NotificationType type, string listName,
+        string subject, string body, string sourceSiteId)
+    {
+        NotificationId = notificationId ?? throw new ArgumentNullException(nameof(notificationId));
+        Type = type;
+        ListName = listName ?? throw new ArgumentNullException(nameof(listName));
+        Subject = subject ?? throw new ArgumentNullException(nameof(subject));
+        Body = body ?? throw new ArgumentNullException(nameof(body));
+        SourceSiteId = sourceSiteId ?? throw new ArgumentNullException(nameof(sourceSiteId));
+    }
+}
diff --git a/tests/ScadaLink.Commons.Tests/Entities/NotificationEntityTests.cs b/tests/ScadaLink.Commons.Tests/Entities/NotificationEntityTests.cs
new file mode 100644
index 0000000..75bc2c5
--- /dev/null
+++ b/tests/ScadaLink.Commons.Tests/Entities/NotificationEntityTests.cs
@@ -0,0 +1,33 @@
+using ScadaLink.Commons.Entities.Notifications;
+using ScadaLink.Commons.Types.Enums;
+
+namespace ScadaLink.Commons.Tests.Entities;
+
+/// <summary>
+/// Verifies the <see cref="Notification"/> outbox entity's constructor defaults
+/// and null-argument guards on required reference-type parameters.
+/// </summary>
+public class NotificationEntityTests
+{
+    [Fact]
+    public void Constructor_SetsDefaults()
+    {
+        var n = new Notification("id-1", NotificationType.Email, "ops-team", "subj", "body", "SiteA");
+        Assert.Equal(NotificationStatus.Pending, n.Status);
+        Assert.Equal(0, n.RetryCount);
+        Assert.Equal("id-1", n.NotificationId);
+        Assert.Equal(NotificationType.Email, n.Type);
+        Assert.Equal("ops-team", n.ListName);
+        Assert.Equal("SiteA", n.SourceSiteId);
+    }
+
+    [Fact]
+    public void Constructor_NullListName_Throws()
+        => Assert.Throws<ArgumentNullException>(
+            () => new Notification("id", NotificationType.Email, null!, "s", "b", "SiteA"));
+
+    [Fact]
+    public void Constructor_NullNotificationId_Throws()
+        => Assert.Throws<ArgumentNullException>(
+            () => new Notification(null!, NotificationType.Email, "list", "s", "b", "SiteA"));
+}