diff --git a/ds-caselaw-ingester/lambda_function.py b/ds-caselaw-ingester/lambda_function.py
index f6b1e17..a3b701e 100644
--- a/ds-caselaw-ingester/lambda_function.py
+++ b/ds-caselaw-ingester/lambda_function.py
@@ -37,7 +37,7 @@ def __init__(self, metadata):
         self.parameters = metadata.get("parameters", {})
 
     @property
-    def is_tdr(self):
+    def is_tdr(self) -> bool:
         return "TDR" in self.parameters.keys()
 
     @property
@@ -86,7 +86,7 @@ def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
 
     @property
-    def originator(self):
+    def originator(self) -> str:
         return self.message.get("parameters", {}).get("originator")
 
     def get_consignment_reference(self):
@@ -100,7 +100,7 @@ def get_consignment_reference(self):
 
         raise InvalidMessageException("Malformed v2 message, please supply a reference")
 
-    def save_s3_response(self, sqs_client, s3_client):
+    def save_s3_response(self, sqs_client, s3_client) -> str:
         s3_bucket = self.message.get("parameters", {}).get("s3Bucket")
         s3_key = self.message.get("parameters", {}).get("s3Key")
         reference = self.get_consignment_reference()
@@ -195,7 +195,7 @@ def modify_filename(original: str, addition: str) -> str:
     return os.path.join(path, new_basename)
 
 
-def all_messages(event) -> List[Message]:
+def all_messages(event) -> list[Message]:
     """All the messages in the SNS event, as Message subclasses"""
     decoder = json.decoder.JSONDecoder()
     messages_as_decoded_json = [decoder.decode(record["Sns"]["Message"]) for record in event["Records"]]
@@ -249,7 +249,7 @@ def extract_docx_filename(metadata: dict, consignment_reference: str) -> str:
         )
 
 
-def extract_lambda_versions(versions: List[Dict[str, str]]) -> List[Tuple[str, str]]:
+def extract_lambda_versions(versions: list[dict[str, str]]) -> list[tuple[str, str]]:
     version_tuples = []
     for d in versions:
         version_tuples += list(d.items())
@@ -501,7 +501,7 @@ def store_metadata(self) -> None:
             value=tdr_metadata["Consignment-Completed-Datetime"],
         )
 
-    def save_files_to_s3(self):
+    def save_files_to_s3(self) -> None:
         sqs_client, s3_client = aws_clients()
         # Determine if there's a word document -- we need to know before we save the tar.gz file
         docx_filename = extract_docx_filename(self.metadata, self.consignment_reference)
@@ -555,7 +555,7 @@ def save_files_to_s3(self):
                 )
 
     @property
-    def metadata_object(self):
+    def metadata_object(self) -> Metadata:
         return Metadata(self.metadata)
 
     def will_publish(self) -> bool:
@@ -574,7 +574,7 @@ def will_publish(self) -> bool:
 
         raise RuntimeError(f"Didn't recognise originator {originator!r}")
 
-    def send_email(self):
+    def send_email(self) -> None:
         originator = self.message.originator
         if originator == "FCL":
             return None
@@ -587,10 +587,10 @@ def send_email(self):
 
         raise RuntimeError(f"Didn't recognise originator {originator!r}")
 
-    def close_tar(self):
+    def close_tar(self) -> None:
         self.tar.close()
 
-    def upload_xml(self):
+    def upload_xml(self) -> None:
         self.updated = self.update_document_xml()
         self.inserted = False if self.updated else self.insert_document_xml()
         if not self.updated and not self.inserted:
@@ -599,7 +599,7 @@ def upload_xml(self):
             )
 
     @property
-    def upload_state(self):
+    def upload_state(self) -> str:
         return "updated" if self.updated else "inserted"