diff --git a/lib/model/query/entities.js b/lib/model/query/entities.js
index 8a4667231..015a276e5 100644
--- a/lib/model/query/entities.js
+++ b/lib/model/query/entities.js
@@ -219,7 +219,21 @@ const _updateEntity = (dataset, entityData, submissionId, submissionDef, submiss
 
   // Figure out the intended baseVersion
   // If this is an offline update with a branchId, the baseVersion value is local to that offline context.
-  const baseEntityDef = await Entities._computeBaseVersion(event.id, dataset, clientEntity, submissionDef, forceOutOfOrderProcessing);
+  let baseEntityDef;
+
+  // Try computing base version.
+  // But if there is a 404.8 not found error, double-check if the entity never existed or was deleted.
+  try {
+    baseEntityDef = await Entities._computeBaseVersion(event.id, dataset, clientEntity, submissionDef, forceOutOfOrderProcessing);
+  } catch (err) {
+    if (err.problemCode === 404.8) {
+      // Look up deleted entity by passing deleted as option argData
+      const deletedEntity = await Entities.getById(dataset.id, clientEntity.uuid, new QueryOptions({ argData: { deleted: 'true' } }));
+      if (deletedEntity.isDefined())
+        throw Problem.user.entityDeleted({ entityUuid: clientEntity.uuid });
+    }
+    throw err;
+  }
 
   // If baseEntityVersion is null, we held a submission and will stop processing now.
   if (baseEntityDef == null)
diff --git a/lib/util/problem.js b/lib/util/problem.js
index 76fde7b55..c5c99c61c 100644
--- a/lib/util/problem.js
+++ b/lib/util/problem.js
@@ -166,6 +166,9 @@ const problems = {
     // entity base version specified in submission does not exist
     entityVersionNotFound: problem(404.9, ({ baseVersion, entityUuid, datasetName }) => `Base version (${baseVersion}) does not exist for entity UUID (${entityUuid}) in dataset (${datasetName}).`),
 
+    // entity has been deleted
+    entityDeleted: problem(404.11, ({ entityUuid }) => `The entity with UUID (${entityUuid}) has been deleted.`),
+
     // { allowed: [ acceptable formats ], got }
     unacceptableFormat: problem(406.1, ({ allowed }) => `Requested format not acceptable; this resource allows: ${allowed.join()}.`),
 
diff --git a/test/integration/api/offline-entities.js b/test/integration/api/offline-entities.js
index 17650a7f8..0cb2baf5f 100644
--- a/test/integration/api/offline-entities.js
+++ b/test/integration/api/offline-entities.js
@@ -1195,7 +1195,42 @@ describe('Offline Entities', () => {
           });
       }));
 
-      // TODO: check deleted entity
+      it('should not process a submission for an entity that has been soft-deleted', testOfflineEntities(async (service, container) => {
+        const asAlice = await service.login('alice');
+        const branchId = uuid();
+
+        // Send the first submission, which will be held in the backlog because the base version is high
+        await asAlice.post('/v1/projects/1/forms/offlineEntity/submissions')
+          .send(testData.instances.offlineEntity.one
+            .replace('branchId=""', `branchId="${branchId}"`)
+            .replace('baseVersion="1"', 'baseVersion="2"')
+          )
+          .set('Content-Type', 'application/xml')
+          .expect(200);
+
+        await exhaust(container);
+
+        let backlogCount = await container.oneFirst(sql`select count(*) from entity_submission_backlog`);
+        backlogCount.should.equal(1);
+
+        // Soft-delete the entity
+        await asAlice.delete('/v1/projects/1/datasets/people/entities/12345678-1234-4123-8234-123456789abc');
+
+        // Process the backlog (count will be 1 but update should not be applied to entity)
+        const processedCount = await container.Entities.processBacklog(true);
+        processedCount.should.equal(1);
+
+        // Check that the backlog count is now 0
+        backlogCount = await container.oneFirst(sql`select count(*) from entity_submission_backlog`);
+        backlogCount.should.equal(0);
+
+        // Check for an entity error on the submission
+        await asAlice.get('/v1/projects/1/forms/offlineEntity/submissions/one/audits')
+          .expect(200)
+          .then(({ body }) => {
+            body[0].details.errorMessage.should.eql('The entity with UUID (12345678-1234-4123-8234-123456789abc) has been deleted.');
+          });
+      }));
     });
   });
 });