diff --git a/app/Models/Audit.php b/app/Models/Audit.php
index 312ff0db..ff6a0fb4 100644
--- a/app/Models/Audit.php
+++ b/app/Models/Audit.php
@@ -4,9 +4,12 @@ declare(strict_types=1);
 
 namespace App\Models;
 
+use App\Models\Concerns\AuditableWithoutOwner;
 use Database\Factories\AuditFactory;
+use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Database\Eloquent\Relations\Relation;
 use Illuminate\Support\Carbon;
 use OwenIt\Auditing\Models\Audit as PackageAuditModel;
 
@@ -31,6 +34,7 @@ use OwenIt\Auditing\Models\Audit as PackageAuditModel;
  * @property-read Organization|null $ownerOrganization
  *
  * @method static AuditFactory factory()
+ * @method static Builder<Audit> whereMissingOwner()
  */
 class Audit extends PackageAuditModel
 {
@@ -52,4 +56,41 @@ class Audit extends PackageAuditModel
     {
         return $this->belongsTo(Organization::class, 'owner_organization_id');
     }
+
+    /**
+     * Whether audits of the given auditable type intentionally have no owner (see AuditableWithoutOwner).
+     */
+    public static function isAuditableTypeWithoutOwner(string $auditableType): bool
+    {
+        $modelClass = Relation::getMorphedModel($auditableType) ?? $auditableType;
+
+        return is_subclass_of($modelClass, AuditableWithoutOwner::class);
+    }
+
+    /**
+     * Auditable types (morph aliases) whose audits intentionally have no owner (see AuditableWithoutOwner).
+     *
+     * @return array<int, string>
+     */
+    public static function getAuditableTypesWithoutOwner(): array
+    {
+        return collect(Relation::morphMap())
+            ->filter(fn (string $modelClass): bool => is_subclass_of($modelClass, AuditableWithoutOwner::class))
+            ->keys()
+            ->values()
+            ->all();
+    }
+
+    /**
+     * Audits that have neither an owner organization nor an owner user, although their auditable type should have one.
+     * These are audits whose owner no longer exists or could not be determined (yet).
+     *
+     * @param  Builder<Audit>  $builder
+     */
+    public function scopeWhereMissingOwner(Builder $builder): void
+    {
+        $builder->whereNull('owner_organization_id')
+            ->whereNull('owner_user_id')
+            ->whereNotIn('auditable_type', self::getAuditableTypesWithoutOwner());
+    }
 }
diff --git a/app/Models/Concerns/AuditableWithoutOwner.php b/app/Models/Concerns/AuditableWithoutOwner.php
new file mode 100644
index 00000000..a32b0ae0
--- /dev/null
+++ b/app/Models/Concerns/AuditableWithoutOwner.php
@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Models\Concerns;
+
+/**
+ * Marks an auditable model whose audits intentionally have no owner (neither an organization nor a user),
+ * either because the model belongs to neither of them, or because the model and its audits have to be kept
+ * when its organization or user is deleted (for example billing records).
+ * Audits of these models are not deleted together with an organization or user,
+ * and are not considered as missing an owner (for example by the audit backfill command).
+ */
+interface AuditableWithoutOwner {}
diff --git a/tests/Unit/Model/AuditModelTest.php b/tests/Unit/Model/AuditModelTest.php
index bc465c7c..6e0950a9 100644
--- a/tests/Unit/Model/AuditModelTest.php
+++ b/tests/Unit/Model/AuditModelTest.php
@@ -5,12 +5,15 @@ declare(strict_types=1);
 namespace Tests\Unit\Model;
 
 use App\Models\Audit;
+use App\Models\Concerns\AuditableWithoutOwner;
 use App\Models\Member;
 use App\Models\Organization;
 use App\Models\Project;
 use App\Models\ProjectMember;
 use App\Models\TimeEntry;
 use App\Models\User;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\Relation;
 use PHPUnit\Framework\Attributes\CoversClass;
 
 #[CoversClass(Audit::class)]
@@ -119,4 +122,52 @@ class AuditModelTest extends ModelTestAbstract
         $this->assertSame(0, Audit::query()->where('auditable_id', $organization->getKey())->count());
         $this->assertSame(1, Audit::query()->where('auditable_id', $otherUser->getKey())->count());
     }
+
+    public function test_auditable_types_without_owner_are_determined_by_the_marker_interface(): void
+    {
+        // Arrange
+        $originalMorphMap = Relation::morphMap();
+        $modelWithoutOwner = new class extends Model implements AuditableWithoutOwner {};
+        Relation::morphMap(['model-without-owner' => $modelWithoutOwner::class]);
+
+        try {
+            // Act
+            $typesWithoutOwner = Audit::getAuditableTypesWithoutOwner();
+            $isWithoutOwner = Audit::isAuditableTypeWithoutOwner('model-without-owner');
+            $isTimeEntryWithoutOwner = Audit::isAuditableTypeWithoutOwner((new TimeEntry)->getMorphClass());
+
+            // Assert
+            $this->assertContains('model-without-owner', $typesWithoutOwner);
+            $this->assertNotContains((new TimeEntry)->getMorphClass(), $typesWithoutOwner);
+            $this->assertTrue($isWithoutOwner);
+            $this->assertFalse($isTimeEntryWithoutOwner);
+        } finally {
+            Relation::morphMap($originalMorphMap, false);
+        }
+    }
+
+    public function test_scope_where_missing_owner_only_returns_audits_without_owner_whose_type_should_have_one(): void
+    {
+        // Arrange
+        $originalMorphMap = Relation::morphMap();
+        $modelWithoutOwner = new class extends Model implements AuditableWithoutOwner {};
+        Relation::morphMap(['model-without-owner' => $modelWithoutOwner::class]);
+        $organization = Organization::factory()->create();
+        $user = User::factory()->create();
+        Audit::query()->delete();
+        $missingOwnerAudit = Audit::factory()->create(['auditable_type' => (new TimeEntry)->getMorphClass()]);
+        Audit::factory()->create(['auditable_type' => (new TimeEntry)->getMorphClass(), 'owner_organization_id' => $organization->getKey()]);
+        Audit::factory()->create(['owner_user_id' => $user->getKey()]);
+        Audit::factory()->create(['auditable_type' => 'model-without-owner']);
+
+        try {
+            // Act
+            $auditIds = Audit::query()->whereMissingOwner()->pluck('id')->all();
+
+            // Assert
+            $this->assertSame([$missingOwnerAudit->getKey()], $auditIds);
+        } finally {
+            Relation::morphMap($originalMorphMap, false);
+        }
+    }
 }