diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_task.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_task.py
index 6f388c7921..42b57a364c 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_task.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/remove_task.py
@@ -18,6 +18,7 @@
 
 import ifcopenshell
 import ifcopenshell.api
+import ifcopenshell.api.nest
 import ifcopenshell.util.element
 
 
@@ -64,28 +65,23 @@ def remove_task(file: ifcopenshell.file, task: ifcopenshell.entity_instance) ->
     )
     if settings["task"].TaskTime:
         file.remove(settings["task"].TaskTime)
+
+    # Handle IfcRelNests.
+    if rels := settings["task"].IsNestedBy:
+        subtasks = rels[0].RelatedObjects
+        # Use batching for optimization.
+        ifcopenshell.api.nest.unassign_object(file, subtasks)
+        for task_ in subtasks:
+            ifcopenshell.api.run("sequence.remove_task", file, task=task_)
+    if settings["task"].Nests:
+        ifcopenshell.api.nest.unassign_object(file, [settings["task"]])
+
     for inverse in file.get_inverse(settings["task"]):
         if inverse.is_a("IfcRelSequence"):
             history = inverse.OwnerHistory
             file.remove(inverse)
             if history:
                 ifcopenshell.util.element.remove_deep2(file, history)
-        elif inverse.is_a("IfcRelNests"):
-            if inverse.RelatingObject == settings["task"]:
-                for related_object in inverse.RelatedObjects:
-                    ifcopenshell.api.run("sequence.remove_task", file, task=related_object)
-            elif not inverse.RelatedObjects:
-                history = inverse.OwnerHistory
-                file.remove(inverse)
-                if history:
-                    ifcopenshell.util.element.remove_deep2(file, history)
-            elif settings["task"] in inverse.RelatedObjects:
-                related_objects = list(inverse.RelatedObjects)
-                related_objects.remove(settings["task"])
-                if not related_objects:
-                    file.remove(inverse)
-                else:
-                    inverse.RelatedObjects = related_objects
         elif inverse.is_a("IfcRelAssignsToControl"):
             if inverse.RelatingControl == settings["task"] or len(inverse.RelatedObjects) == 1:
                 history = inverse.OwnerHistory
diff --git a/src/ifcopenshell-python/test/api/sequence/test_remove_task.py b/src/ifcopenshell-python/test/api/sequence/test_remove_task.py
new file mode 100644
index 0000000000..ed6c5822e3
--- /dev/null
+++ b/src/ifcopenshell-python/test/api/sequence/test_remove_task.py
@@ -0,0 +1,59 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2021 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+import pytest
+import test.bootstrap
+import ifcopenshell.api
+import ifcopenshell.api.nest
+import ifcopenshell.api.sequence
+
+
+# NOTE: sequence module features relies on entities introduced in IFC4
+# therefore no IFC2X3 tests
+class TestRemoveTask(test.bootstrap.IFC4):
+    def test_remove_task(self):
+        self.file.create_entity("IfcProject")
+        work_schedule = ifcopenshell.api.sequence.add_work_schedule(self.file)
+        task = ifcopenshell.api.sequence.add_task(self.file, work_schedule=work_schedule)
+        ifcopenshell.api.sequence.remove_task(self.file, task)
+        assert len(self.file.by_type("IfcTask")) == 0
+
+    def test_remove_task_with_subtasks(self):
+        self.file.create_entity("IfcProject")
+        work_schedule = ifcopenshell.api.sequence.add_work_schedule(self.file)
+        task = ifcopenshell.api.sequence.add_task(self.file, work_schedule=work_schedule)
+        subtask1 = ifcopenshell.api.sequence.add_task(self.file, work_schedule=work_schedule)
+        subtask2 = ifcopenshell.api.sequence.add_task(self.file, work_schedule=work_schedule)
+        ifcopenshell.api.nest.assign_object(self.file, related_objects=[subtask1, subtask2], relating_object=task)
+        ifcopenshell.api.sequence.remove_task(self.file, task)
+        assert len(self.file.by_type("IfcTask")) == 0
+        assert len(self.file.by_type("IfcRelNests")) == 0
+
+    def test_remove_subtask(self):
+        self.file.create_entity("IfcProject")
+        work_schedule = ifcopenshell.api.sequence.add_work_schedule(self.file)
+        task = ifcopenshell.api.sequence.add_task(self.file, work_schedule=work_schedule)
+        subtask1 = ifcopenshell.api.sequence.add_task(self.file, work_schedule=work_schedule)
+        ifcopenshell.api.nest.assign_object(self.file, related_objects=[subtask1], relating_object=task)
+        ifcopenshell.api.sequence.remove_task(self.file, subtask1)
+        assert len(self.file.by_type("IfcTask")) == 1
+        assert len(self.file.by_type("IfcRelNests")) == 0
+
+
+class TestRemoveTaskIFC4X3(test.bootstrap.IFC4X3, TestRemoveTask):
+    pass