diff --git a/scripts/data_prep/prep_dl.py b/scripts/data_prep/prep_dl.py
index e4771a0..bd62d4f 100644
--- a/scripts/data_prep/prep_dl.py
+++ b/scripts/data_prep/prep_dl.py
@@ -1,12 +1,22 @@
 #!/usr/bin/env python
 # coding: utf-8
 
+import os
 import requests
 import pandas as pd
+import hashlib
+
+DIGESTS = {
+    "Output_Areas_Dec_2011_PWC_2022.csv": "4405d695f10556a0f3ff35e36f3aaa1013102da6a4a0c0fffd26554a318faa4f",
+    "LSOA_Dec_2011_PWC_in_England_and_Wales_2022.csv": "4bbc2e6b58302ee274e9c75c6bd9bc068074da08909ca7cffe751c3eb10034e5"
+}
 
 OA_URL = "https://services1.arcgis.com/ESMARspQHYMw9BZ9/arcgis/rest/services/Output_Areas_Dec_2011_PWC_2022/FeatureServer/0/query?where=1%3D1&outFields=*&f=json"
 LSOA_URL = "https://services1.arcgis.com/ESMARspQHYMw9BZ9/arcgis/rest/services/LSOA_Dec_2011_PWC_in_England_and_Wales_2022/FeatureServer/0/query?where=1%3D1&outFields=*&outSR=&f=json"
 
+def check_digest(file_name):
+    digest = hashlib.sha256(open(file_name, 'rb').read()).hexdigest()
+    assert(digest == DIGESTS[os.path.basename(file_name)])
 
 def get_flattened_df(url: str) -> pd.DataFrame:
     """Gets data from API through repeated offset calls until all collected."""
@@ -38,16 +48,22 @@ def main():
     print("Getting LSOA data...")
     df_lsoas = get_flattened_df(LSOA_URL)
     outpath = "Data/dl"
+    oa_file_name = os.path.join(outpath, "Output_Areas_Dec_2011_PWC_2022.csv")
+    lsoa_file_name = os.path.join(outpath, "LSOA_Dec_2011_PWC_in_England_and_Wales_2022.csv")
+    # OA output and check
     df_oas.to_csv(
-        f"{outpath}/Output_Areas_Dec_2011_PWC_2022.csv",
+        oa_file_name,
         index=None,
         line_terminator="\r\n",
     )
+    check_digest(oa_file_name)
+    # LSOA out and check
     df_lsoas.rename(columns={"lsoa11nm": "LSOA11NM", "lsoa11cd": "LSOA11CD"}).to_csv(
-        f"{outpath}/LSOA_Dec_2011_PWC_in_England_and_Wales_2022.csv",
+        lsoa_file_name,
         index=None,
         line_terminator="\r\n",
     )
+    check_digest(lsoa_file_name)
 
 
 if __name__ == "__main__":