diff --git a/src/documents/bulk_edit.py b/src/documents/bulk_edit.py
index aa5b8ea3f..132547704 100644
--- a/src/documents/bulk_edit.py
+++ b/src/documents/bulk_edit.py
@@ -1,3 +1,5 @@
+import itertools
+
 from django.db.models import Q
 from django_q.tasks import async_task
 
@@ -66,6 +68,27 @@ def remove_tag(doc_ids, tag):
     return "OK"
 
 
+def modify_tags(doc_ids, add_tags, remove_tags):
+    qs = Document.objects.filter(id__in=doc_ids)
+    affected_docs = [doc.id for doc in qs]
+
+    DocumentTagRelationship = Document.tags.through
+
+    DocumentTagRelationship.objects.filter(
+        document_id__in=affected_docs,
+        tag_id__in=remove_tags,
+    ).delete()
+
+    DocumentTagRelationship.objects.bulk_create([
+        DocumentTagRelationship(
+            document_id=doc, tag_id=tag) for (doc,tag) in itertools.product(affected_docs, add_tags)
+    ], ignore_conflicts=True)
+
+    async_task("documents.tasks.bulk_rename_files", document_ids=affected_docs)
+
+    return "OK"
+
+
 def delete(doc_ids):
     Document.objects.filter(id__in=doc_ids).delete()
 
diff --git a/src/documents/serialisers.py b/src/documents/serialisers.py
index d9f1833bf..f34176d8a 100644
--- a/src/documents/serialisers.py
+++ b/src/documents/serialisers.py
@@ -217,6 +217,7 @@ class BulkEditSerializer(serializers.Serializer):
             "set_document_type",
             "add_tag",
             "remove_tag",
+            "modify_tags",
             "delete"
         ],
         label="Method",
@@ -225,11 +226,19 @@ class BulkEditSerializer(serializers.Serializer):
 
     parameters = serializers.DictField(allow_empty=True)
 
-    def validate_documents(self, documents):
+    def _validate_document_id_list(self, documents, name="documents"):
+        if not type(documents) == list:
+            raise serializers.ValidationError(f"{name} must be a list")
+        if not all([type(i) == int for i in documents]):
+            raise serializers.ValidationError(f"{name} must be a list of integers")
         count = Document.objects.filter(id__in=documents).count()
         if not count == len(documents):
             raise serializers.ValidationError(
-                "Some documents don't exist or were specified twice.")
+                f"Some documents in {name} don't exist or were specified twice.")
+
+
+    def validate_documents(self, documents):
+        self._validate_document_id_list(documents)
         return documents
 
     def validate_method(self, method):
@@ -241,6 +250,8 @@ class BulkEditSerializer(serializers.Serializer):
             return bulk_edit.add_tag
         elif method == "remove_tag":
             return bulk_edit.remove_tag
+        elif method == "modify_tags":
+            return bulk_edit.modify_tags
         elif method == "delete":
             return bulk_edit.delete
         else:
@@ -283,6 +294,17 @@ class BulkEditSerializer(serializers.Serializer):
         else:
             raise serializers.ValidationError("correspondent not specified")
 
+    def _validate_parameters_modify_tags(self, parameters):
+        if "add_tags" in parameters:
+            self._validate_document_id_list(parameters['add_tags'], "add_tags")
+        else:
+            raise serializers.ValidationError("add_tags not specified")
+
+        if "remove_tags" in parameters:
+            self._validate_document_id_list(parameters['remove_tags'], "remove_tags")
+        else:
+            raise serializers.ValidationError("remove_tags not specified")
+
     def validate(self, attrs):
 
         method = attrs['method']
@@ -294,6 +316,8 @@ class BulkEditSerializer(serializers.Serializer):
             self._validate_parameters_document_type(parameters)
         elif method == bulk_edit.add_tag or method == bulk_edit.remove_tag:
             self._validate_parameters_tags(parameters)
+        elif method == bulk_edit.modify_tags:
+            self._validate_parameters_modify_tags(parameters)
 
         return attrs
 
diff --git a/src/documents/tests/test_api.py b/src/documents/tests/test_api.py
index 0262b6d6a..030de652d 100644
--- a/src/documents/tests/test_api.py
+++ b/src/documents/tests/test_api.py
@@ -743,6 +743,15 @@ class TestBulkEdit(DirectoriesMixin, APITestCase):
         args, kwargs = self.async_task.call_args
         self.assertCountEqual(kwargs['document_ids'], [self.doc4.id])
 
+    def test_modify_tags(self):
+        tag_unrelated = Tag.objects.create(name="unrelated")
+        self.doc2.tags.add(tag_unrelated)
+        self.doc3.tags.add(tag_unrelated)
+        bulk_edit.modify_tags([self.doc2.id, self.doc3.id], add_tags=[self.t2.id], remove_tags=[self.t1.id])
+
+        self.assertCountEqual(list(self.doc2.tags.all()), [self.t2, tag_unrelated])
+        self.assertCountEqual(list(self.doc3.tags.all()), [self.t2, tag_unrelated])
+
     def test_delete(self):
         self.assertEqual(Document.objects.count(), 5)
         bulk_edit.delete([self.doc1.id, self.doc2.id])