diff --git a/apps/transactions/migrations/0002_auto_20191213_1423.py b/apps/transactions/migrations/0002_auto_20191213_1423.py
new file mode 100644
index 0000000..23f6e1d
--- /dev/null
+++ b/apps/transactions/migrations/0002_auto_20191213_1423.py
@@ -0,0 +1,32 @@
+# Generated by Django 3.0 on 2019-12-13 14:23
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('transactions', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='transaction',
+            name='application_id',
+            field=models.IntegerField(blank=True, null=True, verbose_name='application ID'),
+        ),
+        migrations.AlterField(
+            model_name='transaction',
+            name='code',
+            field=models.IntegerField(db_index=True, unique=True, verbose_name='code'),
+        ),
+        migrations.AlterField(
+            model_name='transaction',
+            name='detail_id',
+            field=models.IntegerField(blank=True, null=True),
+        ),
+        migrations.AlterUniqueTogether(
+            name='transaction',
+            unique_together={('application_id', 'detail_id')},
+        ),
+    ]
diff --git a/apps/transactions/migrations/0002_transaction_application_id.py b/apps/transactions/migrations/0002_transaction_application_id.py
deleted file mode 100644
index d9de4b7..0000000
--- a/apps/transactions/migrations/0002_transaction_application_id.py
+++ /dev/null
@@ -1,18 +0,0 @@
-# Generated by Django 3.0 on 2019-12-13 13:52
-
-from django.db import migrations, models
-
-
-class Migration(migrations.Migration):
-
-    dependencies = [
-        ('transactions', '0001_initial'),
-    ]
-
-    operations = [
-        migrations.AddField(
-            model_name='transaction',
-            name='application_id',
-            field=models.IntegerField(blank=True, null=True, verbose_name='application ID'),
-        ),
-    ]
diff --git a/apps/transactions/models.py b/apps/transactions/models.py
index a52ef00..04e4feb 100755
--- a/apps/transactions/models.py
+++ b/apps/transactions/models.py
@@ -52,7 +52,7 @@ class Transaction(models.Model):
         (5, 'done', 'done'),
     )
 
-    code = models.IntegerField(_('code'), blank=False)  # unique random number
+    code = models.IntegerField(_('code'), blank=False, unique=True, db_index=True)  # unique random number
     amount = models.IntegerField(_('amount'), blank=False)
     delay = models.IntegerField(default=0, blank=True)  # number of days for delayed payments
     payer = models.ForeignKey(User, on_delete=models.PROTECT, related_name='payments', blank=True, null=True)
@@ -61,10 +61,13 @@ class Transaction(models.Model):
     create = models.DateTimeField(_('create'), blank=True, null=True, auto_now=True)
     last_update = models.DateTimeField(_('last update'), blank=True, null=True, auto_now=True)
     application_id = models.IntegerField("application ID", blank=True, null=True)
-    detail_id = models.IntegerField(null=True, blank=True, unique=True)  # or better detail url or res number
+    detail_id = models.IntegerField(null=True, blank=True)  # or better detail url or res number
 
     objects = TransactionManager()
 
+    class Meta:
+        unique_together = ('application_id', 'detail_id',)
+
     def set_code(self):
         # TODO: set infinite algorithm
         for code in random.sample(range(10000, 100000), 90000):
diff --git a/apps/transactions/serializers.py b/apps/transactions/serializers.py
index 80cfbe4..1c2241e 100755
--- a/apps/transactions/serializers.py
+++ b/apps/transactions/serializers.py
@@ -8,7 +8,7 @@ from .models import Transaction
 class TransactionSerializer(serializers.ModelSerializer):
     payer = PublicUserSerializer(required=False)
     payee = PublicUserSerializer(required=False, read_only=True)
-    application_id = serializers.IntegerField(required=False, read_only=True)
+    # application_id = serializers.IntegerField(required=False, read_only=True)
 
     class Meta:
         model = Transaction
@@ -24,7 +24,7 @@ class TransactionSerializer(serializers.ModelSerializer):
                   'application_id'
                   )
 
-        read_only_fields = ['last_update', 'code', 'state', 'create', 'detail_id']
+        read_only_fields = ['last_update', 'code', 'state', 'create', 'detail_id', 'application_id']
 
     def create(self, validated_data):
 
diff --git a/apps/transactions/views.py b/apps/transactions/views.py
index 5d10b20..0423184 100755
--- a/apps/transactions/views.py
+++ b/apps/transactions/views.py
@@ -25,7 +25,7 @@ class TransactionList(generics.ListCreateAPIView):
             application_id = None
 
         user = self.request.user
-        serializer.save(payee=user, application_id=application_id)
+        serializer.save(payee=user, application_id=application_id )
 
 
 class TransactionDetail(generics.RetrieveAPIView):