diff --git a/authens/migrations/0002_old_cas_account.py b/authens/migrations/0002_old_cas_account.py
new file mode 100644
index 0000000..b1efde5
--- /dev/null
+++ b/authens/migrations/0002_old_cas_account.py
@@ -0,0 +1,33 @@
+# Generated by Django 3.0.6 on 2020-06-12 17:26
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('authens', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='OldCASAccount',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('cas_login', models.CharField(max_length=1023, verbose_name='ancien login CAS')),
+                ('entrance_year', models.SmallIntegerField(verbose_name='année de création du compte CAS')),
+                ('user', models.OneToOneField(on_delete=django.db.models.deletion.CASCADE, related_name='old_cas_account', to=settings.AUTH_USER_MODEL, verbose_name='utilisateurice')),
+            ],
+            options={
+                'verbose_name': 'Ancien compte CAS',
+                'verbose_name_plural': 'Anciens comptes CAS',
+            },
+        ),
+        migrations.AddConstraint(
+            model_name='oldcasaccount',
+            constraint=models.UniqueConstraint(fields=('cas_login', 'entrance_year'), name='clipper_year_uniqueness'),
+        ),
+    ]
diff --git a/authens/models.py b/authens/models.py
index 90b107c..93a5d61 100644
--- a/authens/models.py
+++ b/authens/models.py
@@ -8,7 +8,7 @@ User = get_user_model()
 class CASAccount(models.Model):
     """Information about CAS accounts.
 
-    A user is given an instance of this model iff she has a CAS account.
+    A user is given an instance of this model iff they have a CAS account.
 
     Instances of this model should only be created by the `ENSCASBackend` authentication
     backend.
@@ -37,3 +37,46 @@ class CASAccount(models.Model):
             "entrance_year": self.entrance_year,
             "user": self.user.username,
         }
+
+
+class OldCASAccount(models.Model):
+    """Information about expired CAS accounts
+
+    A² user is given an instance of this model iff they had a CAS account that expired.
+
+    Instances of this model should not be created with a new user.
+    """
+
+    user = models.OneToOneField(
+        User,
+        verbose_name=_("utilisateurice"),
+        on_delete=models.CASCADE,
+        related_name="old_cas_account",
+    )
+
+    cas_login = models.CharField(
+        verbose_name=_("ancien login CAS"), max_length=1023, blank=False
+    )
+
+    entrance_year = models.SmallIntegerField(
+        verbose_name=_("année de création du compte CAS"), blank=False, null=False
+    )
+
+    class Meta:
+        # `unique_together` to be deprecated soon : we use `constraints`
+        constraints = [
+            models.UniqueConstraint(
+                fields=["cas_login", "entrance_year"], name="clipper_year_uniqueness",
+            )
+        ]
+        verbose_name = _("Ancien compte CAS")
+        verbose_name_plural = _("Anciens comptes CAS")
+
+    def __str__(self):
+        return _(
+            "Ancien compte CAS %(cas_login) (promo %(entrance_year)s) lié à %(user)s"
+        ) % {
+            "cas_login": self.cas_login,
+            "entrance_year": self.entrance_year,
+            "user": self.user.username,
+        }