diff --git a/src/documents/filters.py b/src/documents/filters.py
index fe15c927d..427745424 100644
--- a/src/documents/filters.py
+++ b/src/documents/filters.py
@@ -161,7 +161,9 @@ class ObjectFilter(Filter):
 class InboxFilter(Filter):
     def filter(self, qs, value):
         if value == "true":
-            return qs.filter(tags__is_inbox_tag=True)
+            # A document can have more than one tag flagged as an inbox tag
+            # (nothing enforces uniqueness), so this join can multiply rows.
+            return qs.filter(tags__is_inbox_tag=True).distinct()
         elif value == "false":
             return qs.exclude(tags__is_inbox_tag=True)
         else:
@@ -268,6 +270,10 @@ class CustomFieldsFilter(Filter):
                     for _, option in enumerate(options):
                         if option.get("label").lower().find(value.lower()) != -1:
                             option_ids.extend([option.get("id")])
+            # A document with multiple custom field instances can match more
+            # than one of these OR-ed branches (or the same branch via
+            # different fields), each via its own join to custom_fields --
+            # dedupe explicitly rather than relying on the caller to.
             return (
                 qs.filter(custom_fields__field__name__icontains=value)
                 | qs.filter(custom_fields__value_text__icontains=value)
@@ -280,7 +286,7 @@ class CustomFieldsFilter(Filter):
                 | qs.filter(custom_fields__value_document_ids__icontains=value)
                 | qs.filter(custom_fields__value_select__in=option_ids)
                 | qs.filter(custom_fields__value_long_text__icontains=value)
-            )
+            ).distinct()
         else:
             return qs
 
diff --git a/src/documents/tests/test_api_documents.py b/src/documents/tests/test_api_documents.py
index b0ec51d68..23a150918 100644
--- a/src/documents/tests/test_api_documents.py
+++ b/src/documents/tests/test_api_documents.py
@@ -883,6 +883,62 @@ class TestDocumentApi(DirectoriesMixin, ConsumeTaskMixin, APITestCase):
         results = response.data["results"]
         self.assertEqual(len(results), 3)
 
+    def test_is_in_inbox_filter_no_duplicates_with_multiple_inbox_tags(self) -> None:
+        """
+        GIVEN:
+            - A document tagged with two different inbox tags
+        WHEN:
+            - The document list is filtered by is_in_inbox=true
+        THEN:
+            - The document appears exactly once, not once per matching tag
+        """
+        doc = Document.objects.create(title="doc", checksum="c1")
+        inbox_1 = Tag.objects.create(name="inbox1", is_inbox_tag=True)
+        inbox_2 = Tag.objects.create(name="inbox2", is_inbox_tag=True)
+        doc.tags.add(inbox_1, inbox_2)
+
+        response = self.client.get("/api/documents/?is_in_inbox=true")
+        self.assertEqual(response.status_code, status.HTTP_200_OK)
+        results = response.data["results"]
+        self.assertEqual(len(results), 1)
+        self.assertEqual(results[0]["id"], doc.id)
+
+    def test_custom_fields_icontains_filter_no_duplicates(self) -> None:
+        """
+        GIVEN:
+            - A document with two custom field instances that both match the
+              same custom_fields__icontains search term
+        WHEN:
+            - The document list is filtered by custom_fields__icontains
+        THEN:
+            - The document appears exactly once, not once per matching field
+        """
+        doc = Document.objects.create(title="doc", checksum="c1")
+        field_1 = CustomField.objects.create(
+            name="apple",
+            data_type=CustomField.FieldDataType.STRING,
+        )
+        field_2 = CustomField.objects.create(
+            name="apricot",
+            data_type=CustomField.FieldDataType.STRING,
+        )
+        CustomFieldInstance.objects.create(
+            document=doc,
+            field=field_1,
+            value_text="something",
+        )
+        CustomFieldInstance.objects.create(
+            document=doc,
+            field=field_2,
+            value_text="something else",
+        )
+
+        response = self.client.get("/api/documents/?custom_fields__icontains=ap")
+        self.assertEqual(response.status_code, status.HTTP_200_OK)
+        results = response.data["results"]
+        self.assertEqual(len(results), 1)
+        self.assertEqual(results[0]["id"], doc.id)
+
     def test_custom_field_select_filter(self) -> None:
         """
         GIVEN:
diff --git a/src/documents/views.py b/src/documents/views.py
index 066f8fd8a..750b54248 100644
--- a/src/documents/views.py
+++ b/src/documents/views.py
@@ -1063,9 +1063,16 @@ class DocumentViewSet(
             .values("count"),
             output_field=IntegerField(),
         )
+        # No .distinct() here: nothing in this base queryset can produce
+        # duplicate document rows (select_related below is all FK-to-PK;
+        # permission filtering is a boolean id__in predicate, not a join).
+        # M2M-based filters that *do* introduce a join (e.g. tags__id__in)
+        # already call .distinct() themselves where they need it -- see
+        # ObjectFilter.filter(). A blanket .distinct() here forces the
+        # database to fully sort and dedupe every visible document before
+        # it can apply LIMIT, which is disastrous at scale.
         return (
             Document.objects.filter(root_document__isnull=True)
-            .distinct()
             .order_by("-created", "-id")
             .annotate(effective_content=Coalesce(latest_version_content, F("content")))
             .annotate(num_notes=Coalesce(note_count, 0))