diff --git a/opencodelists/forms.py b/opencodelists/forms.py
index e12ce7e6..5c33f58f 100644
--- a/opencodelists/forms.py
+++ b/opencodelists/forms.py
@@ -77,13 +77,21 @@ def clean_csv_data(self):
         if not f:
             return
 
+        try:
+            data = f.read().decode("utf-8-sig")
+        except UnicodeDecodeError as exception:
+            raise forms.ValidationError(
+                "File could not be read. Please ensure the file contains CSV "
+                "data (not Excel, for example). It should be a text file encoded "
+                f"in the UTF-8 format. Error details: {exception}."
+            )
+
         # Eventually coding system version may be a selectable field, but for now it
-        # just defaults to using the most recent one
+        # just defaults to using the most recent one.
         coding_system = CODING_SYSTEMS[
             self.cleaned_data["coding_system_id"]
         ].get_by_release_or_most_recent()
 
-        data = f.read().decode("utf-8-sig")
         codes = [row[0] for row in csv.reader(StringIO(data)) if row]
         validate_csv_data_codes(coding_system, codes)
         return codes
diff --git a/opencodelists/tests/test_forms.py b/opencodelists/tests/test_forms.py
index c3cda63b..3afc2ef0 100644
--- a/opencodelists/tests/test_forms.py
+++ b/opencodelists/tests/test_forms.py
@@ -1,7 +1,8 @@
 import pytest
 from django.core.exceptions import ValidationError
+from django.core.files.base import ContentFile
 
-from ..forms import MembershipCreateForm, UserPasswordForm
+from ..forms import CodelistCreateForm, MembershipCreateForm, UserPasswordForm
 
 
 def test_userpasswordform_different_passwords():
@@ -48,3 +49,41 @@ def test_membership_create_form_no_user(organisation):
     )
     assert form.is_valid() is False
     assert form.errors == {"user_idenitfier": ["User unknown@test.com does not exist"]}
+
+
+class TestCodelistCreateForm:
+    def _bind_form(self, file):
+        return CodelistCreateForm(
+            data={
+                "name": "test name",
+                "coding_system_id": "snomedct",
+            },
+            files={
+                "csv_data": file,
+            },
+            owner_choices=[],
+        )
+
+    def test_bound_form_valid(self, disorder_of_elbow_codes):
+        valid_csv_data = "\n".join(disorder_of_elbow_codes)
+        file = ContentFile(valid_csv_data.encode("utf-8"))
+        file.name = "valid_data.csv"
+        form = self._bind_form(file)
+
+        assert form.is_valid()
+        assert form.cleaned_data["name"] == "test name"
+        assert form.cleaned_data["coding_system_id"] == "snomedct"
+        assert form.cleaned_data["csv_data"] == disorder_of_elbow_codes
+
+    def test_bound_form_invalid_file_unicode_error(self):
+        invalid_utf8_data = b"\xff\xfe\xfd"
+        file = ContentFile(invalid_utf8_data)
+        file.name = "invalid_data.csv"
+        form = self._bind_form(file)
+
+        assert not form.is_valid()
+        errors = form.errors.get("csv_data")
+        len(errors) == 1
+        assert (
+            "File could not be read. Please ensure the file contains CSV" in errors[0]
+        )