diff --git a/app/dao/fact_billing_dao.py b/app/dao/fact_billing_dao.py
index 367b3e628..3719cc06c 100644
--- a/app/dao/fact_billing_dao.py
+++ b/app/dao/fact_billing_dao.py
@@ -195,7 +195,7 @@ def fetch_billing_data_for_day(process_day, service_id=None):
 def get_rates_for_billing():
     non_letter_rates = [(r.notification_type, r.valid_from, r.rate) for r in
                         Rate.query.order_by(desc(Rate.valid_from)).all()]
-    letter_rates = [(r.start_date, r.crown, r.sheet_count, r.rate) for r in
+    letter_rates = [(r.start_date, r.crown, r.sheet_count, r.rate, r.post_class) for r in
                     LetterRate.query.order_by(desc(LetterRate.start_date)).all()]
     return non_letter_rates, letter_rates
 
@@ -211,11 +211,16 @@ def get_service_ids_that_need_billing_populated(start_date, end_date):
     ).distinct().all()
 
 
-def get_rate(non_letter_rates, letter_rates, notification_type, date, crown=None, letter_page_count=None):
+def get_rate(
+    non_letter_rates, letter_rates, notification_type, date, crown=None, letter_page_count=None, post_class='second'
+):
     if notification_type == LETTER_TYPE:
         if letter_page_count == 0:
             return 0
-        return next(r[3] for r in letter_rates if date > r[0] and crown == r[1] and letter_page_count == r[2])
+        return next(
+            r[3] for r in letter_rates if date > r[0] and crown == r[1]
+            and letter_page_count == r[2] and post_class == r[4]
+        )
     elif notification_type == SMS_TYPE:
         return next(r[2] for r in non_letter_rates if notification_type == r[0] and date > r[1])
     else:
@@ -229,7 +234,8 @@ def update_fact_billing(data, process_day):
                     data.notification_type,
                     process_day,
                     data.crown,
-                    data.letter_page_count)
+                    data.letter_page_count,
+                    "second")
     billing_record = create_billing_record(data, rate, process_day)
     table = FactBilling.__table__
     '''
diff --git a/migrations/versions/0226_new_letter_rates.py b/migrations/versions/0226_new_letter_rates.py
index 7e57d388f..54c45bacc 100644
--- a/migrations/versions/0226_new_letter_rates.py
+++ b/migrations/versions/0226_new_letter_rates.py
@@ -9,11 +9,12 @@ revision = '0226_new_letter_rates'
 down_revision = '0225_another_letter_org'
 
 import uuid
+import pytz
 from datetime import datetime
 from alembic import op
 
 
-start = datetime(2018, 10, 1, 0, 0, tzinfo=timezone.utc)
+start = datetime(2018, 10, 1, 0, 0, tzinfo=pytz.utc)
 
 NEW_RATES = [
     (uuid.uuid4(), start, 1, 0.30, True, 'second'),
diff --git a/tests/app/celery/test_reporting_tasks.py b/tests/app/celery/test_reporting_tasks.py
index a4a21afd7..9b371bf9d 100644
--- a/tests/app/celery/test_reporting_tasks.py
+++ b/tests/app/celery/test_reporting_tasks.py
@@ -23,7 +23,7 @@ def test_reporting_should_have_decorated_tasks_functions():
     assert create_nightly_billing.__wrapped__.__name__ == 'create_nightly_billing'
 
 
-def mocker_get_rate(non_letter_rates, letter_rates, notification_type, date, crown=None, rate_multiplier=None):
+def mocker_get_rate(non_letter_rates, letter_rates, notification_type, date, crown=None, rate_multiplier=None, post_class="second"):
     if notification_type == LETTER_TYPE:
         return Decimal(2.1)
     elif notification_type == SMS_TYPE:
@@ -319,9 +319,10 @@ def test_get_rate_for_letter_latest(notify_db_session):
     non_letter_rates = [(r.notification_type, r.valid_from, r.rate) for r in
                         Rate.query.order_by(desc(Rate.valid_from)).all()]
 
-    # letter rates should be passed into the get_rate function as a tuple of start_date, crown, sheet_count & rate
-    new_letter_rate = (datetime(2017, 12, 1), True, 1, Decimal(0.33))
-    old_letter_rate = (datetime(2016, 12, 1), True, 1, Decimal(0.30))
+    # letter rates should be passed into the get_rate function as a tuple of start_date, crown, sheet_count,
+    # rate and post_class
+    new_letter_rate = (datetime(2017, 12, 1), True, 1, Decimal(0.33), 'second')
+    old_letter_rate = (datetime(2016, 12, 1), True, 1, Decimal(0.30), 'second')
     letter_rates = [new_letter_rate, old_letter_rate]
 
     rate = get_rate(non_letter_rates, letter_rates, LETTER_TYPE, datetime(2018, 1, 1), True, 1)
diff --git a/tests/app/dao/test_ft_billing_dao.py b/tests/app/dao/test_ft_billing_dao.py
index 1eeabeff0..a51feb2ea 100644
--- a/tests/app/dao/test_ft_billing_dao.py
+++ b/tests/app/dao/test_ft_billing_dao.py
@@ -228,7 +228,7 @@ def test_get_rates_for_billing(notify_db_session):
     non_letter_rates, letter_rates = get_rates_for_billing()
 
     assert len(non_letter_rates) == 3
-    assert len(letter_rates) == 10
+    assert len(letter_rates) == 30
 
 
 def test_get_rate(notify_db_session):