diff --git a/priv/repo/seeds.exs b/priv/repo/seeds.exs
index fb102f4..4f99e5b 100644
--- a/priv/repo/seeds.exs
+++ b/priv/repo/seeds.exs
@@ -147,7 +147,6 @@ member_attrs_list = [
     last_name: "Müller",
     email: "hans.mueller@example.de",
     join_date: ~D[2023-01-15],
-    phone_number: "+49301234567",
     city: "München",
     street: "Hauptstraße",
     house_number: "42",
@@ -160,7 +159,6 @@ member_attrs_list = [
     last_name: "Schmidt",
     email: "greta.schmidt@example.de",
     join_date: ~D[2023-02-01],
-    phone_number: "+49309876543",
     city: "Hamburg",
     street: "Lindenstraße",
     house_number: "17",
@@ -174,7 +172,6 @@ member_attrs_list = [
     last_name: "Wagner",
     email: "friedrich.wagner@example.de",
     join_date: ~D[2022-11-10],
-    phone_number: "+49301122334",
     city: "Berlin",
     street: "Kastanienallee",
     house_number: "8",
@@ -186,7 +183,6 @@ member_attrs_list = [
     last_name: "Wagner",
     email: "marianne.wagner@example.de",
     join_date: ~D[2022-11-10],
-    phone_number: "+49301122334",
     city: "Berlin",
     street: "Kastanienallee",
     house_number: "8"
@@ -299,7 +295,6 @@ linked_members = [
     last_name: "Weber",
     email: "maria.weber@example.de",
     join_date: ~D[2023-03-15],
-    phone_number: "+49301357924",
     city: "Frankfurt",
     street: "Goetheplatz",
     house_number: "5",
@@ -313,7 +308,6 @@ linked_members = [
     last_name: "Klein",
     email: "thomas.klein@example.de",
     join_date: ~D[2023-04-01],
-    phone_number: "+49302468135",
     city: "Köln",
     street: "Rheinstraße",
     house_number: "23",
diff --git a/test/membership/member_test.exs b/test/membership/member_test.exs
index 1c4beb1..258d8be 100644
--- a/test/membership/member_test.exs
+++ b/test/membership/member_test.exs
@@ -7,7 +7,6 @@ defmodule Mv.Membership.MemberTest do
       first_name: "John",
       last_name: "Doe",
       email: "john@example.com",
-      phone_number: "+49123456789",
       join_date: ~D[2020-01-01],
       exit_date: nil,
       notes: "Test note",
@@ -17,16 +16,14 @@ defmodule Mv.Membership.MemberTest do
       postal_code: "12345"
     }
 
-    test "First name is required and must not be empty" do
-      attrs = Map.put(@valid_attrs, :first_name, "")
-      assert {:error, %Ash.Error.Invalid{errors: errors}} = Membership.create_member(attrs)
-      assert error_message(errors, :first_name) =~ "must be present"
+    test "First name is optional" do
+      attrs = Map.delete(@valid_attrs, :first_name)
+      assert {:ok, _member} = Membership.create_member(attrs)
     end
 
-    test "Last name is required and must not be empty" do
-      attrs = Map.put(@valid_attrs, :last_name, "")
-      assert {:error, %Ash.Error.Invalid{errors: errors}} = Membership.create_member(attrs)
-      assert error_message(errors, :last_name) =~ "must be present"
+    test "Last name is optional" do
+      attrs = Map.delete(@valid_attrs, :last_name)
+      assert {:ok, _member} = Membership.create_member(attrs)
     end
 
     test "Email is required" do
@@ -41,14 +38,6 @@ defmodule Mv.Membership.MemberTest do
       assert error_message(errors, :email) =~ "is not a valid email"
     end
 
-    test "Phone number is optional but must have a valid format if specified" do
-      attrs = Map.put(@valid_attrs, :phone_number, "abc")
-      assert {:error, %Ash.Error.Invalid{errors: errors}} = Membership.create_member(attrs)
-      assert error_message(errors, :phone_number) =~ "is not a valid phone number"
-      attrs2 = Map.delete(@valid_attrs, :phone_number)
-      assert {:ok, _member} = Membership.create_member(attrs2)
-    end
-
     test "Join date cannot be in the future" do
       attrs = Map.put(@valid_attrs, :join_date, Date.utc_today() |> Date.add(1))
 
diff --git a/test/mv_web/components/sort_header_component_test.exs b/test/mv_web/components/sort_header_component_test.exs
index e199635..6d23ab4 100644
--- a/test/mv_web/components/sort_header_component_test.exs
+++ b/test/mv_web/components/sort_header_component_test.exs
@@ -24,7 +24,6 @@ defmodule MvWeb.Components.SortHeaderComponentTest do
         :house_number,
         :postal_code,
         :city,
-        :phone_number,
         :join_date
       ]
 
@@ -101,7 +100,6 @@ defmodule MvWeb.Components.SortHeaderComponentTest do
       assert has_element?(view, "[data-testid='street'] .opacity-40")
       assert has_element?(view, "[data-testid='house_number'] .opacity-40")
       assert has_element?(view, "[data-testid='postal_code'] .opacity-40")
-      assert has_element?(view, "[data-testid='phone_number'] .opacity-40")
       assert has_element?(view, "[data-testid='join_date'] .opacity-40")
     end
 
diff --git a/test/mv_web/member_live/index_member_fields_display_test.exs b/test/mv_web/member_live/index_member_fields_display_test.exs
index 6b4f50c..c6fd39f 100644
--- a/test/mv_web/member_live/index_member_fields_display_test.exs
+++ b/test/mv_web/member_live/index_member_fields_display_test.exs
@@ -16,7 +16,6 @@ defmodule MvWeb.MemberLive.IndexMemberFieldsDisplayTest do
         house_number: "123",
         postal_code: "12345",
         city: "Berlin",
-        phone_number: "+49123456789",
         join_date: ~D[2020-01-15]
       })
       |> Ash.create()
diff --git a/test/mv_web/member_live/index_test.exs b/test/mv_web/member_live/index_test.exs
index d4f5644..acca9bf 100644
--- a/test/mv_web/member_live/index_test.exs
+++ b/test/mv_web/member_live/index_test.exs
@@ -121,7 +121,6 @@ defmodule MvWeb.MemberLive.IndexTest do
         :house_number,
         :postal_code,
         :city,
-        :phone_number,
         :join_date
       ]