diff --git a/Elwig/Windows/SeasonFinishWindow.xaml.cs b/Elwig/Windows/SeasonFinishWindow.xaml.cs
index 89d7e48..10e79e4 100644
--- a/Elwig/Windows/SeasonFinishWindow.xaml.cs
+++ b/Elwig/Windows/SeasonFinishWindow.xaml.cs
@@ -18,13 +18,15 @@ namespace Elwig.Windows {
         }
 
         protected override async Task OnRenewContext() {
-
+            SeasonInput_ValueChanged(null, null);
         }
 
-        private async void SeasonInput_ValueChanged(object sender, RoutedEventArgs evt) {
-            var s = await Context.Seasons.FindAsync(SeasonInput.Value);
-            var valid = (s != null);
-            CalculateBinsButton.IsEnabled = valid;
+        private async void SeasonInput_ValueChanged(object? sender, RoutedEventArgs? evt) {
+            var s0 = await Context.Seasons.FindAsync(SeasonInput.Value);
+            var s1 = await Context.Seasons.FindAsync(SeasonInput.Value + 1);
+            var valid = (s0 != null);
+            var last = (s1 == null);
+            CalculateBinsButton.IsEnabled = valid && last;
             DeliveryConfirmationButton.IsEnabled = valid;
             OverUnderDeliveryButton.IsEnabled = valid;
         }
@@ -32,6 +34,7 @@ namespace Elwig.Windows {
         private async void CalculateBinsButton_Click(object sender, RoutedEventArgs evt) {
             if (SeasonInput.Value is not int year)
                 return;
+            CalculateBinsButton.IsEnabled = false;
             Mouse.OverrideCursor = Cursors.AppStarting;
             var b = new Billing(year);
             await b.FinishSeason();
@@ -40,6 +43,7 @@ namespace Elwig.Windows {
                 AvoidUnderDeliveriesInput.IsChecked ?? false,
                 HonorGebundenInput.IsChecked ?? false);
             Mouse.OverrideCursor = null;
+            CalculateBinsButton.IsEnabled = true;
         }
 
         private async void DeliveryConfirmationButton_Click(object sender, RoutedEventArgs evt) {