diff --git a/lcl/interfaces/qt5/qtpagecontrol.inc b/lcl/interfaces/qt5/qtpagecontrol.inc
index 87487148c2..46e1b2580e 100644
--- a/lcl/interfaces/qt5/qtpagecontrol.inc
+++ b/lcl/interfaces/qt5/qtpagecontrol.inc
@@ -185,107 +185,6 @@ begin
   end;
 end;
 
-class function TQtWSCustomTabControl.GetDefaultClientRect(
-  const AWinControl: TWinControl; const aLeft, aTop, aWidth, aHeight: integer;
-  var aClientRect: TRect): boolean;
-var
-  dx, dy: integer;
-  ATabWidget: TQtTabWidget;
-  ASize: TSize;
-  HSpace: Integer;
-  Overlap: Integer;
-  VSpace: Integer;
-  BaseHeight: Integer;
-  TabOverLap: Integer;
-  ShiftVertical: Integer;
-begin
-  Result := False;
-  if AWinControl.HandleAllocated then
-  begin
-    if TQtWidget(AWinControl.Handle).ChildOfComplexWidget <> ccwTTabControl then
-    begin
-      ATabWidget := TQtTabWidget(AWinControl.Handle);
-      if ATabWidget.testAttribute(QtWA_PendingResizeEvent) or not ATabWidget.testAttribute(QtWA_Mapped) then
-      begin
-        // we must recalculate aclientrect since we have pending resize event
-        // and clientrect won't be accurate.issue #21805
-        Result := True;
-        dx := GetPixelMetric(QStylePM_DefaultFrameWidth, nil, ATabWidget.Widget);
-        // HSpace := GetPixelMetric(QStylePM_TabBarTabHSpace, nil, nil);
-        VSpace := GetPixelMetric(QStylePM_TabBarTabVSpace, nil, ATabWidget.Widget);
-        Overlap := GetPixelMetric(QStylePM_TabBarBaseOverlap, nil, ATabWidget.Widget);
-        TabOverLap := GetPixelMetric(QStylePM_TabBarTabOverlap, nil, ATabWidget.Widget);
-        BaseHeight := GetPixelMetric(QStylePM_TabBarBaseHeight, nil, ATabWidget.Widget);
-        ShiftVertical := GetPixelMetric(QStylePM_TabBarTabShiftVertical, nil, ATabWidget.Widget);
-
-        // trigger sizing, do not remove
-        ATabWidget.TabBar.sizeHint(@ASize);
-
-        if ATabWidget.getTabPosition in [QTabWidgetNorth, QTabWidgetSouth] then
-        begin
-          if TCustomTabControl(AWinControl).ShowTabs then
-            dy := ATabWidget.TabBar.getHeight
-          else
-            dy := 0;
-
-          if (BaseHeight < ShiftVertical) then
-          begin
-            if (Overlap = 0) then
-            begin
-              BaseHeight := BaseHeight + TabOverLap;
-              dx := dx + (TabOverlap * 2);
-            end else
-            begin
-              BaseHeight := BaseHeight * 2;
-              dx := dx + BaseHeight;
-            end;
-          end;
-
-          if (Overlap > VSpace) then
-            BaseHeight := BaseHeight * 2;
-
-          if (VSpace > TabOverLap) then
-            dx := dx + Overlap;
-
-          aClientRect := Rect(0, 0,
-               Max(0, aWidth - (BaseHeight * 2)),
-               Max(0, aHeight - dx  - dy));
-        end else
-        begin
-          if TCustomTabControl(AWinControl).ShowTabs then
-            dy := ATabWidget.TabBar.getWidth
-          else
-            dy := 0;
-
-          VSpace := 0;
-          HSpace := 0;
-
-          if BaseHeight < ShiftVertical then
-            VSpace := TabOverLap - BaseHeight;
-          if (Overlap < dx) then
-          begin
-            VSpace := OverLap;
-            if OverLap = 0 then
-            begin
-              VSpace := TabOverLap * 2;
-              HSpace := BaseHeight;
-            end;
-          end;
-
-          aClientRect := Rect(0,0,
-               Max(0, aWidth - dx  - dy - VSpace),
-               Max(0, aHeight - (dx + Overlap + VSpace + HSpace)));
-        end;
-      end;
-    end;
-  end else
-  begin
-    dx := GetPixelMetric(QStylePM_TabBarBaseHeight, nil, nil);
-    aClientRect := Rect(0,0, Max(0, aWidth - (dx * 2)), Max(0, aHeight - (dx * 2)));
-    Result := True;
-  end;
-end;
-
 class procedure TQtWSCustomTabControl.AddPage(const ATabControl: TCustomTabControl;
   const AChild: TCustomPage; const AIndex: integer);
 var
diff --git a/lcl/interfaces/qt5/qtwscomctrls.pp b/lcl/interfaces/qt5/qtwscomctrls.pp
index 3a0a85569c..b35edc2a57 100644
--- a/lcl/interfaces/qt5/qtwscomctrls.pp
+++ b/lcl/interfaces/qt5/qtwscomctrls.pp
@@ -53,9 +53,6 @@ type
   published
     class function  CreateHandle(const AWinControl: TWinControl;
           const AParams: TCreateParams): TLCLHandle; override;
-    class function GetDefaultClientRect(const AWinControl: TWinControl;
-             const {%H-}aLeft, {%H-}aTop, aWidth, aHeight: integer; var aClientRect: TRect
-             ): boolean; override;
     class procedure AddPage(const ATabControl: TCustomTabControl;
       const AChild: TCustomPage; const AIndex: integer); override;
     class procedure MovePage(const ATabControl: TCustomTabControl;
diff --git a/lcl/interfaces/qt6/qtpagecontrol.inc b/lcl/interfaces/qt6/qtpagecontrol.inc
index 87487148c2..46e1b2580e 100644
--- a/lcl/interfaces/qt6/qtpagecontrol.inc
+++ b/lcl/interfaces/qt6/qtpagecontrol.inc
@@ -185,107 +185,6 @@ begin
   end;
 end;
 
-class function TQtWSCustomTabControl.GetDefaultClientRect(
-  const AWinControl: TWinControl; const aLeft, aTop, aWidth, aHeight: integer;
-  var aClientRect: TRect): boolean;
-var
-  dx, dy: integer;
-  ATabWidget: TQtTabWidget;
-  ASize: TSize;
-  HSpace: Integer;
-  Overlap: Integer;
-  VSpace: Integer;
-  BaseHeight: Integer;
-  TabOverLap: Integer;
-  ShiftVertical: Integer;
-begin
-  Result := False;
-  if AWinControl.HandleAllocated then
-  begin
-    if TQtWidget(AWinControl.Handle).ChildOfComplexWidget <> ccwTTabControl then
-    begin
-      ATabWidget := TQtTabWidget(AWinControl.Handle);
-      if ATabWidget.testAttribute(QtWA_PendingResizeEvent) or not ATabWidget.testAttribute(QtWA_Mapped) then
-      begin
-        // we must recalculate aclientrect since we have pending resize event
-        // and clientrect won't be accurate.issue #21805
-        Result := True;
-        dx := GetPixelMetric(QStylePM_DefaultFrameWidth, nil, ATabWidget.Widget);
-        // HSpace := GetPixelMetric(QStylePM_TabBarTabHSpace, nil, nil);
-        VSpace := GetPixelMetric(QStylePM_TabBarTabVSpace, nil, ATabWidget.Widget);
-        Overlap := GetPixelMetric(QStylePM_TabBarBaseOverlap, nil, ATabWidget.Widget);
-        TabOverLap := GetPixelMetric(QStylePM_TabBarTabOverlap, nil, ATabWidget.Widget);
-        BaseHeight := GetPixelMetric(QStylePM_TabBarBaseHeight, nil, ATabWidget.Widget);
-        ShiftVertical := GetPixelMetric(QStylePM_TabBarTabShiftVertical, nil, ATabWidget.Widget);
-
-        // trigger sizing, do not remove
-        ATabWidget.TabBar.sizeHint(@ASize);
-
-        if ATabWidget.getTabPosition in [QTabWidgetNorth, QTabWidgetSouth] then
-        begin
-          if TCustomTabControl(AWinControl).ShowTabs then
-            dy := ATabWidget.TabBar.getHeight
-          else
-            dy := 0;
-
-          if (BaseHeight < ShiftVertical) then
-          begin
-            if (Overlap = 0) then
-            begin
-              BaseHeight := BaseHeight + TabOverLap;
-              dx := dx + (TabOverlap * 2);
-            end else
-            begin
-              BaseHeight := BaseHeight * 2;
-              dx := dx + BaseHeight;
-            end;
-          end;
-
-          if (Overlap > VSpace) then
-            BaseHeight := BaseHeight * 2;
-
-          if (VSpace > TabOverLap) then
-            dx := dx + Overlap;
-
-          aClientRect := Rect(0, 0,
-               Max(0, aWidth - (BaseHeight * 2)),
-               Max(0, aHeight - dx  - dy));
-        end else
-        begin
-          if TCustomTabControl(AWinControl).ShowTabs then
-            dy := ATabWidget.TabBar.getWidth
-          else
-            dy := 0;
-
-          VSpace := 0;
-          HSpace := 0;
-
-          if BaseHeight < ShiftVertical then
-            VSpace := TabOverLap - BaseHeight;
-          if (Overlap < dx) then
-          begin
-            VSpace := OverLap;
-            if OverLap = 0 then
-            begin
-              VSpace := TabOverLap * 2;
-              HSpace := BaseHeight;
-            end;
-          end;
-
-          aClientRect := Rect(0,0,
-               Max(0, aWidth - dx  - dy - VSpace),
-               Max(0, aHeight - (dx + Overlap + VSpace + HSpace)));
-        end;
-      end;
-    end;
-  end else
-  begin
-    dx := GetPixelMetric(QStylePM_TabBarBaseHeight, nil, nil);
-    aClientRect := Rect(0,0, Max(0, aWidth - (dx * 2)), Max(0, aHeight - (dx * 2)));
-    Result := True;
-  end;
-end;
-
 class procedure TQtWSCustomTabControl.AddPage(const ATabControl: TCustomTabControl;
   const AChild: TCustomPage; const AIndex: integer);
 var
diff --git a/lcl/interfaces/qt6/qtwscomctrls.pp b/lcl/interfaces/qt6/qtwscomctrls.pp
index c5db8532d4..5d4a9dee0e 100644
--- a/lcl/interfaces/qt6/qtwscomctrls.pp
+++ b/lcl/interfaces/qt6/qtwscomctrls.pp
@@ -51,9 +51,6 @@ type
   published
     class function  CreateHandle(const AWinControl: TWinControl;
           const AParams: TCreateParams): TLCLHandle; override;
-    class function GetDefaultClientRect(const AWinControl: TWinControl;
-             const {%H-}aLeft, {%H-}aTop, aWidth, aHeight: integer; var aClientRect: TRect
-             ): boolean; override;
     class procedure AddPage(const ATabControl: TCustomTabControl;
       const AChild: TCustomPage; const AIndex: integer); override;
     class procedure MovePage(const ATabControl: TCustomTabControl;