diff --git a/Elwig/Dialogs/TareCorrectionDialog.xaml.cs b/Elwig/Dialogs/TareCorrectionDialog.xaml.cs
index e56532d..736a397 100644
--- a/Elwig/Dialogs/TareCorrectionDialog.xaml.cs
+++ b/Elwig/Dialogs/TareCorrectionDialog.xaml.cs
@@ -8,10 +8,11 @@ namespace Elwig.Dialogs {
         public int ActualTare { get; private set; }
         public int TargetTare { get; private set; }
 
-        public TareCorrectionDialog(int actualTare, int? targetTare = null) {
+        public TareCorrectionDialog(int? actualTare, int? targetTare = null) {
             InitializeComponent();
-            ActualTare = actualTare;
-            TargetTare = targetTare ?? actualTare;
+            ActualTare = actualTare ?? 0;
+            TargetTare = targetTare ?? actualTare ?? 0;
+            ActualTareInput.IsReadOnly = actualTare != null;
             ActualTareInput.Text = ActualTare.ToString();
             TargetTareInput.Text = TargetTare.ToString();
             TargetTareInput.SelectAll();
@@ -19,12 +20,13 @@ namespace Elwig.Dialogs {
 
         private void ConfirmButton_Click(object sender, RoutedEventArgs evt) {
             DialogResult = true;
+            ActualTare = int.Parse(ActualTareInput.Text);
             TargetTare = int.Parse(TargetTareInput.Text);
             Close();
         }
 
         private void UpdateButtons() {
-            ConfirmButton.IsEnabled = TargetTareInput.Text.Length > 0;
+            ConfirmButton.IsEnabled = ActualTareInput.Text.Length > 0 && TargetTareInput.Text.Length > 0;
         }
 
         private void TareInput_TextChanged(object sender, TextChangedEventArgs evt) {
diff --git a/Elwig/Helpers/Utils.cs b/Elwig/Helpers/Utils.cs
index 4aaab1a..6c736c3 100644
--- a/Elwig/Helpers/Utils.cs
+++ b/Elwig/Helpers/Utils.cs
@@ -303,7 +303,7 @@ namespace Elwig.Helpers {
             return d.ShowDialog() == true ? (d.Weight, d.Reason) : null;
         }
 
-        public static int? ShowTareCorrectionDialog(int actualTare, int? targetTare = null) {
+        public static int? ShowTareCorrectionDialog(int? actualTare, int? targetTare = null) {
             var d = new TareCorrectionDialog(actualTare, targetTare);
             return d.ShowDialog() == true ? d.TargetTare - d.ActualTare : null;
         }
diff --git a/Elwig/Services/DeliveryService.cs b/Elwig/Services/DeliveryService.cs
index 32361da..abc0fa8 100644
--- a/Elwig/Services/DeliveryService.cs
+++ b/Elwig/Services/DeliveryService.cs
@@ -37,7 +37,7 @@ namespace Elwig.Services {
             vm.GradationKmwString = "";
 
             vm.Weight = null;
-            vm.ActualTare = 0;
+            vm.ActualTare = null;
             vm.TargetTare = null;
             vm.Tare = null;
             vm.IsManualWeighing = false;
@@ -58,9 +58,9 @@ namespace Elwig.Services {
             vm.WineOrigin = ControlUtils.GetItemFromSourceWithPk(vm.WineOriginSource, p.HkId) as WineOrigin;
 
             vm.Weight = p.Weight;
-            vm.ActualTare = p.WeighingInfo.Tare ?? 0;
+            vm.ActualTare = p.WeighingInfo.Tare;
             vm.TargetTare = vm.ActualTare + p.WeighingInfo.TareCorrection;
-            vm.Tare = vm.TargetTare ?? (vm.ActualTare != 0 ? vm.ActualTare : null);
+            vm.Tare = vm.TargetTare ?? (vm.ActualTare is int t && t != 0 ? t : null);
             vm.IsManualWeighing = p.IsManualWeighing;
             vm.IsNetWeight = p.IsNetWeight;
 
diff --git a/Elwig/ViewModels/DeliveryAdminViewModel.cs b/Elwig/ViewModels/DeliveryAdminViewModel.cs
index f68ae8c..16c0765 100644
--- a/Elwig/ViewModels/DeliveryAdminViewModel.cs
+++ b/Elwig/ViewModels/DeliveryAdminViewModel.cs
@@ -125,7 +125,7 @@ namespace Elwig.ViewModels {
             get => int.TryParse(TareString?.Replace(Utils.GroupSeparator, "").Replace(" kg", ""), out var w) ? w : null;
             set => TareString = value == null ? "-" : $"{value:N0} kg{(TargetTare != null ? "*" : "")}";
         }
-        public int ActualTare;
+        public int? ActualTare;
         public int? TargetTare;
         [ObservableProperty]
         private bool _isManualWeighing;
diff --git a/Elwig/Windows/DeliveryAdminWindow.xaml.cs b/Elwig/Windows/DeliveryAdminWindow.xaml.cs
index 6282a87..ec03c8a 100644
--- a/Elwig/Windows/DeliveryAdminWindow.xaml.cs
+++ b/Elwig/Windows/DeliveryAdminWindow.xaml.cs
@@ -614,7 +614,7 @@ namespace Elwig.Windows {
             ClearOriginalValues();
             ClearDefaultValues();
             ViewModel.FillInputs(p);
-            CorrectTareButton.Visibility = !ViewModel.IsReceipt && (ViewModel.ActualTare != 0 || ViewModel.IsUnloadingBox) ? Visibility.Visible : Visibility.Hidden;
+            CorrectTareButton.Visibility = !ViewModel.IsReceipt && ((ViewModel.ActualTare is int t && t != 0) || ViewModel.IsUnloadingBox) ? Visibility.Visible : Visibility.Hidden;
             FinishInputFilling();
         }
 
@@ -625,13 +625,13 @@ namespace Elwig.Windows {
         }
 
         private void CorrectTareButton_Click(object sender, RoutedEventArgs evt) {
-            var lastCorrection = (ViewModel.TargetTare ?? ViewModel.ActualTare) - ViewModel.ActualTare;
+            var lastCorrection = (ViewModel.TargetTare ?? ViewModel.ActualTare ?? 0) - (ViewModel.ActualTare ?? 0);
             var correction = Utils.ShowTareCorrectionDialog(ViewModel.ActualTare, ViewModel.TargetTare);
             if (correction == null) return;
             ViewModel.Weight += lastCorrection - correction;
-            ViewModel.TargetTare = correction == 0 ? null : ViewModel.ActualTare + correction;
-            ViewModel.Tare = ViewModel.TargetTare ?? ViewModel.ActualTare;
             if (ViewModel.WeighingData is string s) {
+                ViewModel.TargetTare = correction == 0 ? null : (ViewModel.ActualTare ?? 0) + correction;
+                ViewModel.Tare = ViewModel.TargetTare ?? ViewModel.ActualTare;
                 var obj = JsonNode.Parse(s)!.AsObject();
                 if (correction == 0) {
                     obj.Remove("tare_correction");
@@ -673,16 +673,16 @@ namespace Elwig.Windows {
         private void OnWeighingResult(IScale scale, WeighingResult res) {
             if ((res.NetWeight ?? 0) > 0 && res.FullWeighingId != null) {
                 ViewModel.Weight = res.NetWeight;
-                ViewModel.ActualTare = res.TareWeight ?? 0;
+                ViewModel.ActualTare = res.TareWeight;
                 ViewModel.TargetTare = null;
-                ViewModel.Tare = ViewModel.ActualTare != 0 ? ViewModel.ActualTare : null;
+                ViewModel.Tare = ViewModel.ActualTare is int t && t != 0 ? t : null;
                 ViewModel.ScaleTerminalId = scale.ScaleTerminalId;
                 ViewModel.WeighingData = res.ToJson().ToJsonString();
                 ViewModel.ManualWeighingReason = null;
                 ManualWeighingInput.IsChecked = false;
             } else {
                 ViewModel.Weight = null;
-                ViewModel.ActualTare = 0;
+                ViewModel.ActualTare = null;
                 ViewModel.TargetTare = null;
                 ViewModel.Tare = null;
                 ViewModel.ScaleTerminalId = null;
@@ -1410,7 +1410,7 @@ namespace Elwig.Windows {
         private void UnloadingInput_Checked(object sender, RoutedEventArgs evt) {
             if (!IsEditing && !IsCreating) return;
             if (!ViewModel.IsReceipt)
-                CorrectTareButton.Visibility = ViewModel.ActualTare != 0 || ViewModel.IsUnloadingBox ? Visibility.Visible : Visibility.Hidden;
+                CorrectTareButton.Visibility = (ViewModel.ActualTare is int t && t != 0) || ViewModel.IsUnloadingBox ? Visibility.Visible : Visibility.Hidden;
             var mod = ViewModel.Modifiers.ToList();
             var source = ViewModel.ModifiersSource.ToList();
             if (App.Client.IsMatzen) {