diff --git a/ucalc/Data/BillingLoader.cs b/ucalc/Data/BillingLoader.cs
index 7553604..9f076b0 100644
--- a/ucalc/Data/BillingLoader.cs
+++ b/ucalc/Data/BillingLoader.cs
@@ -71,11 +71,11 @@ namespace UCalc.Data
 
     public static class BillingLoader
     {
-        private static string AsString(JObject parent, string name, bool optional = false)
+        private static string AsString(JObject parent, string name, string defaultValue = null)
         {
-            if (optional && (parent[name]?.Type ?? JTokenType.Null) == JTokenType.Null)
+            if (defaultValue != null && (parent[name]?.Type ?? JTokenType.Null) == JTokenType.Null)
             {
-                return "";
+                return defaultValue;
             }
 
             return parent[name]?.Value<string>() ??
@@ -89,7 +89,7 @@ namespace UCalc.Data
 
         private static DateTime? AsDateOptional(JObject parent, string name)
         {
-            var str = AsString(parent, name, true);
+            var str = AsString(parent, name, "");
             if (string.IsNullOrEmpty(str))
             {
                 return null;
@@ -104,8 +104,13 @@ namespace UCalc.Data
                    throw new JsonException($"Cannot read {parent.Path}.{name} as integer");
         }
 
-        private static bool AsBool(JObject parent, string name)
+        private static bool AsBool(JObject parent, string name, bool? defaultValue = null)
         {
+            if (defaultValue != null && (parent[name]?.Type ?? JTokenType.Null) == JTokenType.Null)
+            {
+                return defaultValue.Value;
+            }
+
             return parent[name]?.Value<bool>() ??
                    throw new JsonException($"Cannot read {parent.Path}.{name} as bool");
         }
@@ -118,7 +123,7 @@ namespace UCalc.Data
 
         private static decimal? AsDecimalOptional(JObject parent, string name)
         {
-            var str = AsString(parent, name, true);
+            var str = AsString(parent, name, "");
             if (string.IsNullOrEmpty(str))
             {
                 return null;
@@ -187,7 +192,7 @@ namespace UCalc.Data
                 billing.Landlord.Salutation = (Salutation) AsInt(landlord, "salutation");
                 billing.Landlord.Name = AsString(landlord, "name");
                 billing.Landlord.Phone = AsString(landlord, "phone");
-                billing.Landlord.MailAddress = AsString(landlord, "mail");
+                billing.Landlord.MailAddress = AsString(landlord, "mail", "");
                 LoadAddress(landlord, "address", billing.Landlord.Address);
                 LoadBankAccount(landlord, "account", billing.Landlord.BankAccount);
 
@@ -207,8 +212,8 @@ namespace UCalc.Data
                         EntryDate = AsDateOptional(tenant, "entry_date"),
                         DepartureDate = AsDateOptional(tenant, "departure_date"),
                         PaidRent = AsDecimal(tenant, "paid_rent"),
-                        CustomMessage1 = AsString(tenant, "message1", true),
-                        CustomMessage2 = AsString(tenant, "message2", true)
+                        CustomMessage1 = AsString(tenant, "message1", ""),
+                        CustomMessage2 = AsString(tenant, "message2", "")
                     };
                     LoadBankAccount(tenant, "account", targetTenant.BankAccount);
 
@@ -266,7 +271,7 @@ namespace UCalc.Data
                                 Details = details
                             };
                         }).ToList(),
-                        DisplayInBill = AsBool(cost, "display")
+                        DisplayInBill = AsBool(cost, "display", false)
                     };
 
                     billing.Costs.Add(targetCost);
diff --git a/ucalc/Models/BankAccountProperty.cs b/ucalc/Models/BankAccountProperty.cs
index dfac11c..e00c4d4 100644
--- a/ucalc/Models/BankAccountProperty.cs
+++ b/ucalc/Models/BankAccountProperty.cs
@@ -4,15 +4,25 @@ namespace UCalc.Models
 {
     public class BankAccountProperty : NestedProperty
     {
-        public NotEmptyStringProperty Iban { get; }
-        public NotEmptyStringProperty Bic { get; }
-        public NotEmptyStringProperty BankName { get; }
+        public ValueProperty<string> Iban { get; }
+        public ValueProperty<string> Bic { get; }
+        public ValueProperty<string> BankName { get; }
 
-        public BankAccountProperty(Model model, Property parent, BankAccount data) : base(model, parent)
+        public BankAccountProperty(Model model, Property parent, BankAccount data, bool belongsToTenant) : base(model,
+            parent)
         {
-            Iban = Add(new NotEmptyStringProperty(model, this, "IBAN", data.Iban));
-            Bic = Add(new NotEmptyStringProperty(model, this, "BIC", data.Bic));
-            BankName = Add(new NotEmptyStringProperty(model, this, "Name der Bank", data.BankName));
+            if (belongsToTenant)
+            {
+                Iban = Add(new AlwaysValidProperty<string>(model, this, "IBAN", data.Iban));
+                Bic = Add(new AlwaysValidProperty<string>(model, this, "BIC", data.Bic));
+                BankName = Add(new AlwaysValidProperty<string>(model, this, "Name der Bank", data.BankName));
+            }
+            else
+            {
+                Iban = Add(new NotEmptyStringProperty(model, this, "IBAN", data.Iban));
+                Bic = Add(new NotEmptyStringProperty(model, this, "BIC", data.Bic));
+                BankName = Add(new NotEmptyStringProperty(model, this, "Name der Bank", data.BankName));
+            }
         }
     }
 }
\ No newline at end of file
diff --git a/ucalc/Models/LandlordProperty.cs b/ucalc/Models/LandlordProperty.cs
index ea22858..aca7e93 100644
--- a/ucalc/Models/LandlordProperty.cs
+++ b/ucalc/Models/LandlordProperty.cs
@@ -6,7 +6,7 @@ namespace UCalc.Models
     {
         public SalutationProperty Salutation { get; }
         public NotEmptyStringProperty Name { get; }
-        public NotEmptyStringProperty MailAddress { get; }
+        public AlwaysValidProperty<string> MailAddress { get; }
         public NotEmptyStringProperty Phone { get; }
         public AddressProperty Address { get; }
         public BankAccountProperty BankAccount { get; }
@@ -15,10 +15,10 @@ namespace UCalc.Models
         {
             Salutation = Add(new SalutationProperty(model, this, "Anrede", data.Salutation));
             Name = Add(new NotEmptyStringProperty(model, this, "Name", data.Name));
-            MailAddress = Add(new NotEmptyStringProperty(model, this, "Email Adresse", data.MailAddress));
+            MailAddress = Add(new AlwaysValidProperty<string>(model, this, "Email Adresse", data.MailAddress));
             Phone = Add(new NotEmptyStringProperty(model, this, "Telefonnummer", data.Phone));
             Address = Add(new AddressProperty(model, this, data.Address));
-            BankAccount = Add(new BankAccountProperty(model, this, data.BankAccount));
+            BankAccount = Add(new BankAccountProperty(model, this, data.BankAccount, false));
         }
     }
 }
\ No newline at end of file
diff --git a/ucalc/Models/TenantProperty.cs b/ucalc/Models/TenantProperty.cs
index 0f38a57..08fc205 100644
--- a/ucalc/Models/TenantProperty.cs
+++ b/ucalc/Models/TenantProperty.cs
@@ -212,7 +212,7 @@ namespace UCalc.Models
             Salutation = Add(new SalutationProperty(model, this, "Anrede", data.Salutation));
             Name = Add(new NotEmptyStringProperty(model, this, "Name", data.Name));
             PersonCount = Add(new NaturalNumberProperty(model, this, "Personenanzahl", data.PersonCount));
-            BankAccount = Add(new BankAccountProperty(model, this, data.BankAccount));
+            BankAccount = Add(new BankAccountProperty(model, this, data.BankAccount, true));
             EntryDate = Add(new EntryDateProperty(model, this, "Einzugsdatum", data.EntryDate));
             DepartureDate = Add(new DepatureDateProperty(model, this, "Auszugsdatum", data.DepartureDate));
             RentedFlats = Add(new RentedFlatsProperty(model, this, data.RentedFlats, flatToProperty));
diff --git a/ucalc/PrintWindow.xaml.cs b/ucalc/PrintWindow.xaml.cs
index feb2615..ad92fd3 100644
--- a/ucalc/PrintWindow.xaml.cs
+++ b/ucalc/PrintWindow.xaml.cs
@@ -188,7 +188,12 @@ namespace UCalc
             }
 
             AddText(
-                $"{Billing.Landlord.Salutation.AsString()} {Billing.Landlord.Name}\n{DateTime.Now.ToString(Constants.DateFormat)}\n\n{Billing.Landlord.Address.Street} {Billing.Landlord.Address.HouseNumber}\n{Billing.Landlord.Address.Postcode} {Billing.Landlord.Address.City}\nTelefon: {Billing.Landlord.Phone}\nEmail: {Billing.Landlord.MailAddress}");
+                $"{Billing.Landlord.Salutation.AsString()} {Billing.Landlord.Name}\n{DateTime.Now.ToString(Constants.DateFormat)}\n\n{Billing.Landlord.Address.Street} {Billing.Landlord.Address.HouseNumber}\n{Billing.Landlord.Address.Postcode} {Billing.Landlord.Address.City}\nTelefon: {Billing.Landlord.Phone}");
+
+            if (!string.IsNullOrEmpty(Billing.Landlord.MailAddress))
+            {
+                AddText($"Email: {Billing.Landlord.MailAddress}");
+            }
 
             AddLineBreaks(2);