diff --git a/app/dao/date_util.py b/app/dao/date_util.py
index 77a46c69e..1b795226c 100644
--- a/app/dao/date_util.py
+++ b/app/dao/date_util.py
@@ -63,8 +63,9 @@ def get_current_financial_year_start_year():
     return financial_year_start
 
 
-def which_financial_year(start_date):
-    if start_date <= get_april_fools(int(start_date.strftime('%Y'))):
-        return int(start_date.strftime('%Y')) - 1
+def get_financial_year_for_datetime(start_date):
+    year = int(start_date.strftime('%Y'))
+    if start_date < get_april_fools(year):
+        return year - 1
     else:
-        return int(start_date.strftime('%Y'))
+        return year
diff --git a/app/dao/fact_billing_dao.py b/app/dao/fact_billing_dao.py
index 40e4b5a57..07f8f15ae 100644
--- a/app/dao/fact_billing_dao.py
+++ b/app/dao/fact_billing_dao.py
@@ -9,7 +9,7 @@ from app import db
 from app.dao.date_util import (
     get_april_fools as financial_year_start,
     get_financial_year,
-    which_financial_year
+    get_financial_year_for_datetime
 )
 
 from app.models import (
@@ -33,7 +33,7 @@ from app.utils import get_london_midnight_in_utc
 
 def fetch_sms_free_allowance_remainder(start_date):
     # ASSUMPTION: AnnualBilling has been populated for year.
-    billing_year = which_financial_year(start_date)
+    billing_year = get_financial_year_for_datetime(start_date)
     print(billing_year)
     start_of_year = convert_utc_to_bst(financial_year_start(billing_year))
     query = db.session.query(
@@ -60,7 +60,7 @@ def fetch_sms_free_allowance_remainder(start_date):
 def fetch_sms_billing_for_all_services(start_date, end_date):
 
     # ASSUMPTION: AnnualBilling has been populated for year.
-    billing_year = which_financial_year(start_date)
+    billing_year = get_financial_year_for_datetime(start_date)
     free_allowance_remainder = fetch_sms_free_allowance_remainder(start_date).subquery()
     sms_billable_units = func.sum(FactBilling.billable_units * FactBilling.rate_multiplier)
     sms_remainder = func.coalesce(free_allowance_remainder.c.sms_remainder, AnnualBilling.free_sms_fragment_limit)
diff --git a/tests/app/dao/test_date_utils.py b/tests/app/dao/test_date_utils.py
index afa2b4897..b76f87466 100644
--- a/tests/app/dao/test_date_utils.py
+++ b/tests/app/dao/test_date_utils.py
@@ -2,7 +2,12 @@ from datetime import datetime
 
 import pytest
 
-from app.dao.date_util import get_financial_year, get_april_fools, get_month_start_and_end_date_in_utc
+from app.dao.date_util import (
+    get_financial_year,
+    get_april_fools,
+    get_month_start_and_end_date_in_utc,
+    get_financial_year_for_datetime,
+)
 
 
 def test_get_financial_year():
@@ -29,3 +34,13 @@ def test_get_month_start_and_end_date_in_utc(month, year, expected_start, expect
     result = get_month_start_and_end_date_in_utc(month_year)
     assert result[0] == expected_start
     assert result[1] == expected_end
+
+
+@pytest.mark.parametrize("dt, fy", [
+    (datetime(2018, 3, 31, 23, 0, 0), 2018),
+    (datetime(2019, 3, 31, 22, 59, 59), 2018),
+    (datetime(2019, 3, 31, 23, 0, 0), 2019),
+    (datetime(2020, 3, 31, 22, 59, 0), 2019),
+])
+def test_get_financial_year_for_datetime(dt, fy):
+    assert get_financial_year_for_datetime(dt) == fy