diff --git a/app/dao/jobs_dao.py b/app/dao/jobs_dao.py
index e22c1c709..c40311d16 100644
--- a/app/dao/jobs_dao.py
+++ b/app/dao/jobs_dao.py
@@ -2,14 +2,17 @@ import uuid
 from datetime import datetime, timedelta
 
 from flask import current_app
+from notifications_utils.letter_timings import letter_can_be_cancelled
 from notifications_utils.statsd_decorators import statsd
 from sqlalchemy import (
     asc,
     desc,
     func,
 )
+from sqlalchemy.testing import not_in_
 
 from app import db
+from app.dao.dao_utils import transactional
 from app.utils import midnight_n_days_ago
 from app.models import (
     Job,
@@ -18,7 +21,11 @@ from app.models import (
     LETTER_TYPE,
     Notification,
     Template,
-    ServiceDataRetention
+    ServiceDataRetention,
+    NOTIFICATION_SENDING,
+    NOTIFICATION_CREATED,
+    NOTIFICATION_CANCELLED,
+    JOB_STATUS_CANCELLED
 )
 from app.variables import LETTER_TEST_API_FILENAME
 
@@ -148,16 +155,37 @@ def dao_get_jobs_older_than_data_retention(notification_types):
     return jobs
 
 
-def dao_get_all_letter_jobs():
-    return db.session.query(
-        Job
-    ).join(
-        Job.template
-    ).filter(
-        Template.template_type == LETTER_TYPE,
-        # test letter jobs (or from research mode services) are created with a different filename,
-        # exclude them so we don't see them on the send to CSV
-        Job.original_file_name != LETTER_TEST_API_FILENAME
-    ).order_by(
-        desc(Job.created_at)
-    ).all()
+@transactional
+def dao_cancel_letter_job(service_id, job_id):
+    if can_cancel_letter_job(job_id, service_id):
+        number_of_notifications_cancelled = Notification.query.filter(
+            Notification.job_id == job_id
+        ).update({'status': NOTIFICATION_CANCELLED,
+                  'updated_at': datetime.utcnow(),
+                  'billable_units': 0})
+        # calling this 2x - pass job into can_cancel_letter_job
+        job = dao_get_job_by_service_id_and_job_id(service_id, job_id)
+        job.job_status = JOB_STATUS_CANCELLED
+        dao_update_job(job)
+        return number_of_notifications_cancelled
+
+
+def can_cancel_letter_job(job_id, service_id):
+    job = dao_get_job_by_service_id_and_job_id(service_id, job_id)
+    # assert is a letter job
+    # assert job status == finished???
+    # Notifications are not in pending-virus-check
+    count_notifications_in_sending = Notification.query.filter(
+        Notification.job_id == job_id,
+        Notification.status.not_in_('created', 'pending-virus-check', 'cancelled')
+    ).count()
+    if count_notifications_in_sending > 0:
+        return False
+    if not letter_can_be_cancelled(NOTIFICATION_CREATED, job.created_at):
+        return False
+    else:
+        return True
+
+
+
+
diff --git a/app/job/rest.py b/app/job/rest.py
index 20f37efed..1d125c007 100644
--- a/app/job/rest.py
+++ b/app/job/rest.py
@@ -5,6 +5,7 @@ from flask import (
     request,
     current_app
 )
+from notifications_utils.letter_timings import letter_can_be_cancelled
 
 from app.aws.s3 import get_job_metadata_from_s3
 from app.dao.jobs_dao import (
@@ -13,7 +14,8 @@ from app.dao.jobs_dao import (
     dao_get_job_by_service_id_and_job_id,
     dao_get_jobs_by_service_id,
     dao_get_future_scheduled_job_by_id_and_service_id,
-    dao_get_notification_outcomes_for_job)
+    dao_get_notification_outcomes_for_job, dao_cancel_letter_job
+)
 from app.dao.fact_notification_status_dao import fetch_notification_statuses_for_job
 from app.dao.services_dao import dao_fetch_service_by_id
 from app.dao.templates_dao import dao_get_template_by_id
diff --git a/tests/app/dao/test_jobs_dao.py b/tests/app/dao/test_jobs_dao.py
index 524d17f8e..500bd90f0 100644
--- a/tests/app/dao/test_jobs_dao.py
+++ b/tests/app/dao/test_jobs_dao.py
@@ -14,6 +14,7 @@ from app.dao.jobs_dao import (
     dao_get_future_scheduled_job_by_id_and_service_id,
     dao_get_notification_outcomes_for_job,
     dao_get_jobs_older_than_data_retention,
+    dao_cancel_letter_job
 )
 from app.models import (
     Job,
@@ -308,3 +309,17 @@ def assert_job_stat(job, result, sent, delivered, failed):
     assert result.sent == sent
     assert result.delivered == delivered
     assert result.failed == failed
+
+
+def test_dao_cancel_letter_job_does_not_allow_cancel_if_notification_in_sending(sample_job):
+    create_notification(template=sample_job.template, job=sample_job, status='sending')
+    create_notification(template=sample_job.template, job=sample_job, status='created')
+    assert not dao_cancel_letter_job(service_id=sample_job.service_id, job_id=sample_job.id)
+
+
+def test_dao_cancel_letter_job_updates_notifications_and_job_to_cancelled(sample_job):
+    notification = create_notification(template=sample_job.template, job=sample_job, status='created')
+    assert dao_cancel_letter_job(service_id=sample_job.service_id, job_id=sample_job.id) == 1
+    assert notification.status == 'cancelled'
+    assert sample_job.job_status == 'cancelled'
+