diff --git a/services/domain/Big.Application/HerregistratieReminderSweep.cs b/services/domain/Big.Application/HerregistratieReminderSweep.cs
index ddc3d82..626b8e8 100644
--- a/services/domain/Big.Application/HerregistratieReminderSweep.cs
+++ b/services/domain/Big.Application/HerregistratieReminderSweep.cs
@@ -13,6 +13,18 @@ namespace Big.Application;
 /// </summary>
 public sealed class HerregistratieReminderSweep(IRegistrationStore store, TimeProvider clock)
 {
-    public Task<IReadOnlyList<RegistrationId>> SweepAsync(CancellationToken ct = default)
-        => Task.FromResult<IReadOnlyList<RegistrationId>>([]); // RED stub
+    public async Task<IReadOnlyList<RegistrationId>> SweepAsync(CancellationToken ct = default)
+    {
+        var due = await store.FindDueForHerregistratieReminderAsync(clock.GetUtcNow(), ct);
+
+        var reminded = new List<RegistrationId>(due.Count);
+        foreach (var registration in due)
+        {
+            registration.MarkHerregistratieReminderVerstuurd();
+            await store.SaveAsync(registration, ct);
+            reminded.Add(registration.Id);
+        }
+
+        return reminded;
+    }
 }