diff --git a/docs/source/interfaces/isis_sans/Settings Tab.rst b/docs/source/interfaces/isis_sans/Settings Tab.rst
index 105162676b96..f80878d8a86d 100644
--- a/docs/source/interfaces/isis_sans/Settings Tab.rst	
+++ b/docs/source/interfaces/isis_sans/Settings Tab.rst	
@@ -104,9 +104,6 @@ use 8, 9, 10, 12, 14, 16, 20, 21, 22.
 Compatibility Mode
 """"""""""""""""""
 
-*As of version 6.11 of Mantid, this feature is no longer enabled by default.
-It should be considered deprecated and will be removed in a future release.*
-
 The previous SANS GUI converted event-mode data to histogram-mode early into
 processing. This used the time-of-flight binning parameters specified by the
 user or copied the monitor binning.
diff --git a/docs/source/release/v6.11.0/SANS/New_features/38053.rst b/docs/source/release/v6.11.0/SANS/New_features/38053.rst
deleted file mode 100644
index 15e37be62a2c..000000000000
--- a/docs/source/release/v6.11.0/SANS/New_features/38053.rst
+++ /dev/null
@@ -1 +0,0 @@
-- The :ref:`compatibility_mode` feature in the ISIS SANS GUI is no longer selected by default. This feature should be considered deprecated and will be removed completely in a future release.
\ No newline at end of file
diff --git a/scripts/Interface/ui/sans_isis/sans_data_processor_window.ui b/scripts/Interface/ui/sans_isis/sans_data_processor_window.ui
index 8c64576eeae8..559449734ff3 100644
--- a/scripts/Interface/ui/sans_isis/sans_data_processor_window.ui
+++ b/scripts/Interface/ui/sans_isis/sans_data_processor_window.ui
@@ -95,7 +95,7 @@ QGroupBox::title {
       <item>
        <widget class="QStackedWidget" name="main_stacked_widget">
         <property name="currentIndex">
-         <number>1</number>
+         <number>0</number>
         </property>
         <widget class="QWidget" name="run_page">
          <layout class="QVBoxLayout" name="verticalLayout_3">
@@ -988,7 +988,7 @@ QGroupBox::title {
                      <bool>true</bool>
                     </property>
                     <property name="checked">
-                     <bool>false</bool>
+                     <bool>true</bool>
                     </property>
                     <layout class="QGridLayout" name="gridLayout_16">
                      <item row="0" column="0">
diff --git a/scripts/SANS/sans/state/StateObjects/StateCompatibility.py b/scripts/SANS/sans/state/StateObjects/StateCompatibility.py
index 4b0f2f8eaae6..a4f57416ed83 100644
--- a/scripts/SANS/sans/state/StateObjects/StateCompatibility.py
+++ b/scripts/SANS/sans/state/StateObjects/StateCompatibility.py
@@ -28,7 +28,7 @@
 class StateCompatibility(metaclass=JsonSerializable):
     def __init__(self):
         super(StateCompatibility, self).__init__()
-        self.use_compatibility_mode = False  # : Bool
+        self.use_compatibility_mode = True  # : Bool
         self.use_event_slice_optimisation = False  # : Bool
         self.time_rebin_string = ""  # Str
 
diff --git a/scripts/test/SANS/gui_logic/state_gui_model_test.py b/scripts/test/SANS/gui_logic/state_gui_model_test.py
index e076266bff3f..49ea1a669f5a 100644
--- a/scripts/test/SANS/gui_logic/state_gui_model_test.py
+++ b/scripts/test/SANS/gui_logic/state_gui_model_test.py
@@ -35,9 +35,9 @@ def test_that_default_instrument_is_NoInstrument(self):
     # ------------------------------------------------------------------------------------------------------------------
     # Compatibility Mode
     # ------------------------------------------------------------------------------------------------------------------
-    def test_that_default_compatibility_mode_is_false(self):
+    def test_that_default_compatibility_mode_is_true(self):
         state_gui_model = StateGuiModel(AllStates())
-        self.assertFalse(state_gui_model.compatibility_mode)
+        self.assertTrue(state_gui_model.compatibility_mode)
 
     def test_that_can_set_compatibility_mode(self):
         state_gui_model = StateGuiModel(AllStates())