diff --git a/backend/address2UPRN/tests/test_csv.py b/backend/address2UPRN/tests/test_csv.py
index 70e7a9f9..73d94388 100644
--- a/backend/address2UPRN/tests/test_csv.py
+++ b/backend/address2UPRN/tests/test_csv.py
@@ -1,12 +1,24 @@
 # tests/test_address_to_uprn_csv.py
 
 import csv
+import time
 import pytest
 from pathlib import Path
 from backend.address2UPRN.main import get_uprn
 
 FIXTURE_PATH = Path(__file__).parent / "test_data.csv"
 
+# Delay between live EPC API calls to stay under the (undocumented) rate limit.
+# Each parametrized case fires at least one EPC request; without throttling,
+# GitHub-hosted runners burst fast enough to hit 429s.
+EPC_THROTTLE_SECONDS = 1.0
+
+
+@pytest.fixture(autouse=True)
+def _throttle_epc_requests():
+    yield
+    time.sleep(EPC_THROTTLE_SECONDS)
+
 
 def load_test_cases():
     with open(FIXTURE_PATH, newline="", encoding="utf-8") as f: