diff --git a/lib/mv_web/live/components/member_filter_component.ex b/lib/mv_web/live/components/member_filter_component.ex
index 657cb02..f5f99ea 100644
--- a/lib/mv_web/live/components/member_filter_component.ex
+++ b/lib/mv_web/live/components/member_filter_component.ex
@@ -9,7 +9,8 @@ defmodule MvWeb.Components.MemberFilterComponent do
 
   - Uses `div` panel instead of `ul.menu/li` structure to avoid DaisyUI menu styles
     (padding, display, hover, font sizes) that would interfere with form controls.
-  - Filter controls are form elements (fieldset, radio inputs), not menu items.
+  - Filter controls are form elements (fieldset with legend, radio inputs), not menu items.
+    Uses semantic `<fieldset>` and `<legend>` for proper accessibility and form structure.
   - Dropdown stays open when clicking filter segments to allow multiple filter changes.
   - Uses `phx-change` on form for radio inputs instead of individual `phx-click` events.
 
@@ -88,7 +89,8 @@ defmodule MvWeb.Components.MemberFilterComponent do
     <!--
         NOTE: We use a div panel instead of ul.menu/li structure to avoid DaisyUI menu styles
         (padding, display, hover, font sizes) that would interfere with our form controls.
-        Filter controls are form elements (fieldset, radio inputs), not menu items.
+        Filter controls are form elements (fieldset with legend, radio inputs), not menu items.
+        We use semantic fieldset/legend structure for proper accessibility.
         We use relative/absolute positioning instead of DaisyUI dropdown classes to have
         full control over the open/close state via LiveView.
       -->
@@ -107,11 +109,11 @@ defmodule MvWeb.Components.MemberFilterComponent do
             <div class="text-xs font-semibold opacity-70 mb-2 uppercase tracking-wider">
               {gettext("Payments")}
             </div>
-            <div class="grid grid-cols-[1fr_auto] items-center gap-3 py-2">
-              <label class="text-sm font-medium" for="payment-filter">
+            <fieldset class="grid grid-cols-[1fr_auto] items-center gap-3 py-2 border-0 p-0 m-0 min-w-0">
+              <legend class="text-sm font-medium col-start-1 float-left w-auto">
                 {gettext("Payment Status")}
-              </label>
-              <fieldset class="join" aria-label={gettext("Payment status filter")}>
+              </legend>
+              <div class="join col-start-2">
                 <label
                   class={"#{payment_filter_label_class(@cycle_status_filter, nil)} has-[:focus-visible]:ring-2 has-[:focus-visible]:ring-primary"}
                   for="payment-filter-all"
@@ -156,8 +158,8 @@ defmodule MvWeb.Components.MemberFilterComponent do
                   <.icon name="hero-x-circle" class="h-5 w-5" />
                   <span class="text-xs">{gettext("Unpaid")}</span>
                 </label>
-              </fieldset>
-            </div>
+              </div>
+            </fieldset>
           </div>
           
     <!-- Custom Fields Group -->
@@ -166,20 +168,14 @@ defmodule MvWeb.Components.MemberFilterComponent do
               {gettext("Custom Fields")}
             </div>
             <div class="max-h-60 overflow-y-auto pr-2">
-              <div
+              <fieldset
                 :for={custom_field <- @boolean_custom_fields}
-                class="grid grid-cols-[1fr_auto] items-center gap-3 py-2 border-b border-base-200 last:border-0"
+                class="grid grid-cols-[1fr_auto] items-center gap-3 py-2 border-b border-base-200 last:border-0 border-0 p-0 m-0 min-w-0"
               >
-                <label
-                  class="text-sm font-medium"
-                  for={"custom-boolean-filter-#{custom_field.id}"}
-                >
+                <legend class="text-sm font-medium col-start-1 float-left w-auto">
                   {custom_field.name}
-                </label>
-                <fieldset
-                  class="join"
-                  aria-label={gettext("Filter by %{name}", name: custom_field.name)}
-                >
+                </legend>
+                <div class="join col-start-2">
                   <label
                     class={"#{boolean_filter_label_class(@boolean_filters, custom_field.id, nil)} has-[:focus-visible]:ring-2 has-[:focus-visible]:ring-primary"}
                     for={"custom-boolean-filter-#{custom_field.id}-all"}
@@ -228,8 +224,8 @@ defmodule MvWeb.Components.MemberFilterComponent do
                     <.icon name="hero-x-circle" class="h-5 w-5" />
                     <span class="text-xs">{gettext("No")}</span>
                   </label>
-                </fieldset>
-              </div>
+                </div>
+              </fieldset>
             </div>
           </div>
           
diff --git a/lib/mv_web/live/member_live/index.ex b/lib/mv_web/live/member_live/index.ex
index 9fc9cdf..41ef275 100644
--- a/lib/mv_web/live/member_live/index.ex
+++ b/lib/mv_web/live/member_live/index.ex
@@ -778,9 +778,32 @@ defmodule MvWeb.MemberLive.Index do
       |> Ash.Query.new()
       |> Ash.Query.select(@overview_fields)
 
-    # Load custom field values for visible custom fields (based on user selection)
+    # Load custom field values for visible custom fields AND active boolean filters
+    # This ensures boolean filters work even when the custom field is not visible in overview
     visible_custom_field_ids = socket.assigns[:visible_custom_field_ids] || []
-    query = load_custom_field_values(query, visible_custom_field_ids)
+
+    # Get IDs of active boolean filters (whitelisted against boolean_custom_fields)
+    # Convert boolean_custom_fields list to map for efficient lookup (consistent with maybe_update_boolean_filters)
+    boolean_custom_fields_map =
+      socket.assigns.boolean_custom_fields
+      |> Map.new(fn cf -> {to_string(cf.id), cf} end)
+
+    active_boolean_filter_ids =
+      socket.assigns.boolean_custom_field_filters
+      |> Map.keys()
+      |> Enum.filter(fn id_str ->
+        # Validate UUID format and check against whitelist
+        String.length(id_str) <= @max_uuid_length &&
+          match?({:ok, _}, Ecto.UUID.cast(id_str)) &&
+          Map.has_key?(boolean_custom_fields_map, id_str)
+      end)
+
+    # Union of visible IDs and active filter IDs
+    ids_to_load =
+      (visible_custom_field_ids ++ active_boolean_filter_ids)
+      |> Enum.uniq()
+
+    query = load_custom_field_values(query, ids_to_load)
 
     # Load membership fee cycles for status display
     query = MembershipFeeStatus.load_cycles_for_members(query, socket.assigns.show_current_cycle)
@@ -1233,35 +1256,43 @@ defmodule MvWeb.MemberLive.Index do
       |> Map.new(fn cf -> {to_string(cf.id), cf} end)
 
     # Parse all boolean filter parameters
+    # Security: Use reduce_while to abort early after @max_boolean_filters to prevent DoS attacks
+    # This protects CPU/Parsing costs, not just memory/state
+    # We count processed parameters (not just valid filters) to protect against parsing DoS
     prefix_length = String.length(@boolean_filter_prefix)
 
-    filters =
+    {filters, total_processed} =
       params
       |> Enum.filter(fn {key, _value} -> String.starts_with?(key, @boolean_filter_prefix) end)
-      |> Enum.reduce(%{}, fn {key, value_str}, acc ->
-        process_boolean_filter_param(
-          key,
-          value_str,
-          prefix_length,
-          boolean_custom_fields,
-          acc
-        )
+      |> Enum.reduce_while({%{}, 0}, fn {key, value_str}, {acc, count} ->
+        if count >= @max_boolean_filters do
+          Logger.warning(
+            "Too many boolean filter parameters in request (#{count} processed), limiting to #{@max_boolean_filters} to prevent DoS"
+          )
+
+          {:halt, {acc, count}}
+        else
+          new_acc =
+            process_boolean_filter_param(
+              key,
+              value_str,
+              prefix_length,
+              boolean_custom_fields,
+              acc
+            )
+
+          # Increment counter for each processed parameter (DoS protection)
+          # Note: We count processed params, not just valid filters, to protect parsing costs
+          {:cont, {new_acc, count + 1}}
+        end
       end)
 
-    # Security: Limit number of filters to prevent DoS attacks
-    # Maximum @max_boolean_filters boolean filters allowed per request
-    filters =
-      if map_size(filters) > @max_boolean_filters do
-        Logger.warning(
-          "Too many boolean filters requested: #{map_size(filters)}, limiting to #{@max_boolean_filters}"
-        )
-
-        filters
-        |> Enum.take(@max_boolean_filters)
-        |> Enum.into(%{})
-      else
-        filters
-      end
+    # Log additional warning if we hit the limit
+    if total_processed >= @max_boolean_filters do
+      Logger.warning(
+        "Boolean filter limit reached: processed #{total_processed} parameters, accepted #{map_size(filters)} valid filters (max: #{@max_boolean_filters})"
+      )
+    end
 
     assign(socket, :boolean_custom_field_filters, filters)
   end
@@ -1340,8 +1371,8 @@ defmodule MvWeb.MemberLive.Index do
   # This ensures no raw user input is ever passed to filter functions.
   #
   # Returns:
-  # - `:true` for "true" string
-  # - `:false` for "false" string
+  # - `true` for "true" string
+  # - `false` for "false" string
   # - `nil` for any other value
   defp determine_boolean_filter("true"), do: true
   defp determine_boolean_filter("false"), do: false
diff --git a/priv/gettext/de/LC_MESSAGES/default.po b/priv/gettext/de/LC_MESSAGES/default.po
index 83d8ed0..3369548 100644
--- a/priv/gettext/de/LC_MESSAGES/default.po
+++ b/priv/gettext/de/LC_MESSAGES/default.po
@@ -1925,11 +1925,6 @@ msgstr "Validierung fehlgeschlagen: %{message}"
 msgid "Close"
 msgstr "Schließen"
 
-#: lib/mv_web/live/components/member_filter_component.ex
-#, elixir-autogen, elixir-format
-msgid "Filter by %{name}"
-msgstr "Filtern nach %{name}"
-
 #: lib/mv_web/live/components/member_filter_component.ex
 #, elixir-autogen, elixir-format
 msgid "Filter members"
@@ -1945,12 +1940,17 @@ msgstr "Mitgliedsfilter"
 msgid "Payment Status"
 msgstr "Bezahlstatus"
 
-#: lib/mv_web/live/components/member_filter_component.ex
-#, elixir-autogen, elixir-format, fuzzy
-msgid "Payment status filter"
-msgstr "Bezahlstatusfilter"
-
 #: lib/mv_web/live/components/member_filter_component.ex
 #, elixir-autogen, elixir-format
 msgid "Reset"
 msgstr "Zurücksetzen"
+
+#~ #: lib/mv_web/live/components/member_filter_component.ex
+#~ #, elixir-autogen, elixir-format
+#~ msgid "Filter by %{name}"
+#~ msgstr "Filtern nach %{name}"
+
+#~ #: lib/mv_web/live/components/member_filter_component.ex
+#~ #, elixir-autogen, elixir-format, fuzzy
+#~ msgid "Payment status filter"
+#~ msgstr "Bezahlstatusfilter"
diff --git a/priv/gettext/default.pot b/priv/gettext/default.pot
index 87acf6b..fb50446 100644
--- a/priv/gettext/default.pot
+++ b/priv/gettext/default.pot
@@ -1926,11 +1926,6 @@ msgstr ""
 msgid "Close"
 msgstr ""
 
-#: lib/mv_web/live/components/member_filter_component.ex
-#, elixir-autogen, elixir-format
-msgid "Filter by %{name}"
-msgstr ""
-
 #: lib/mv_web/live/components/member_filter_component.ex
 #, elixir-autogen, elixir-format
 msgid "Filter members"
@@ -1946,11 +1941,6 @@ msgstr ""
 msgid "Payment Status"
 msgstr ""
 
-#: lib/mv_web/live/components/member_filter_component.ex
-#, elixir-autogen, elixir-format
-msgid "Payment status filter"
-msgstr ""
-
 #: lib/mv_web/live/components/member_filter_component.ex
 #, elixir-autogen, elixir-format
 msgid "Reset"
diff --git a/priv/gettext/en/LC_MESSAGES/default.po b/priv/gettext/en/LC_MESSAGES/default.po
index 81135b2..37a7a0d 100644
--- a/priv/gettext/en/LC_MESSAGES/default.po
+++ b/priv/gettext/en/LC_MESSAGES/default.po
@@ -780,6 +780,7 @@ msgstr ""
 msgid "Payment Data"
 msgstr ""
 
+#: lib/mv_web/live/components/member_filter_component.ex
 #: lib/mv_web/live/member_live/form.ex
 #, elixir-autogen, elixir-format
 msgid "Payments"
@@ -1925,11 +1926,6 @@ msgstr ""
 msgid "Close"
 msgstr ""
 
-#: lib/mv_web/live/components/member_filter_component.ex
-#, elixir-autogen, elixir-format
-msgid "Filter by %{name}"
-msgstr ""
-
 #: lib/mv_web/live/components/member_filter_component.ex
 #, elixir-autogen, elixir-format
 msgid "Filter members"
@@ -1940,21 +1936,11 @@ msgstr ""
 msgid "Member filter"
 msgstr ""
 
-#: lib/mv_web/live/components/member_filter_component.ex
-#, elixir-autogen, elixir-format, fuzzy
-msgid "Payment"
-msgstr ""
-
 #: lib/mv_web/live/components/member_filter_component.ex
 #, elixir-autogen, elixir-format, fuzzy
 msgid "Payment Status"
 msgstr ""
 
-#: lib/mv_web/live/components/member_filter_component.ex
-#, elixir-autogen, elixir-format, fuzzy
-msgid "Payment status filter"
-msgstr ""
-
 #: lib/mv_web/live/components/member_filter_component.ex
 #, elixir-autogen, elixir-format
 msgid "Reset"
@@ -1986,6 +1972,11 @@ msgstr ""
 #~ msgid "Regular"
 #~ msgstr ""
 
+#~ #: lib/mv_web/live/components/member_filter_component.ex
+#~ #, elixir-autogen, elixir-format, fuzzy
+#~ msgid "Payment"
+#~ msgstr ""
+
 #~ #: lib/mv_web/live/contribution_period_live/show.ex
 #~ #, elixir-autogen, elixir-format
 #~ msgid "Current"
@@ -2207,6 +2198,11 @@ msgstr ""
 #~ msgid "Contributions for %{name}"
 #~ msgstr ""
 
+#~ #: lib/mv_web/live/components/member_filter_component.ex
+#~ #, elixir-autogen, elixir-format, fuzzy
+#~ msgid "Payment status filter"
+#~ msgstr ""
+
 #~ #: lib/mv_web/live/contribution_type_live/index.ex
 #~ #, elixir-autogen, elixir-format
 #~ msgid "Family"
@@ -2251,3 +2247,8 @@ msgstr ""
 #~ #, elixir-autogen, elixir-format
 #~ msgid "About Contribution Types"
 #~ msgstr ""
+
+#~ #: lib/mv_web/live/components/member_filter_component.ex
+#~ #, elixir-autogen, elixir-format
+#~ msgid "Filter by %{name}"
+#~ msgstr ""
diff --git a/test/mv_web/member_live/index_test.exs b/test/mv_web/member_live/index_test.exs
index daa377f..3391b86 100644
--- a/test/mv_web/member_live/index_test.exs
+++ b/test/mv_web/member_live/index_test.exs
@@ -1526,6 +1526,44 @@ defmodule MvWeb.MemberLive.IndexTest do
       refute html =~ "FalseMember"
     end
 
+    test "boolean filter works even when custom field is not visible in overview", %{conn: conn} do
+      conn = conn_with_oidc_user(conn)
+
+      # Create boolean field with show_in_overview: false
+      boolean_field = create_boolean_custom_field(%{show_in_overview: false})
+
+      _member_with_true =
+        create_member_with_boolean_value(%{first_name: "TrueMember"}, boolean_field, true)
+
+      _member_with_false =
+        create_member_with_boolean_value(%{first_name: "FalseMember"}, boolean_field, false)
+
+      {:ok, _member_without_value} =
+        Mv.Membership.Member
+        |> Ash.Changeset.for_create(:create_member, %{
+          first_name: "NoValue",
+          last_name: "Member",
+          email: "novalue.member.#{System.unique_integer([:positive])}@example.com"
+        })
+        |> Ash.create()
+
+      # Test that filter works even though field is not visible in overview
+      {:ok, _view, html_true} =
+        live(conn, "/members?bf_#{boolean_field.id}=true")
+
+      assert html_true =~ "TrueMember"
+      refute html_true =~ "FalseMember"
+      refute html_true =~ "NoValue"
+
+      # Test false filter
+      {:ok, _view, html_false} =
+        live(conn, "/members?bf_#{boolean_field.id}=false")
+
+      assert html_false =~ "FalseMember"
+      refute html_false =~ "TrueMember"
+      refute html_false =~ "NoValue"
+    end
+
     test "boolean custom field appears in filter dropdown after being added", %{conn: conn} do
       conn = conn_with_oidc_user(conn)