diff --git a/lib/api/category.dart b/lib/api/category.dart
index ee7f78d..4fe0f22 100644
--- a/lib/api/category.dart
+++ b/lib/api/category.dart
@@ -22,18 +22,36 @@ class WalletCategory {
   factory WalletCategory.fromJson(Map<String, dynamic> json) =>
       _$WalletCategoryFromJson(json);
 
+  /// Default [WalletCategory] instance for json_serializable
+  factory WalletCategory.unknown() => WalletCategory(
+        name: "Unknown",
+        id: -1,
+        icon: Icons.question_mark,
+        color: Colors.green,
+      );
+
   /// User-defined name
+  @JsonKey(defaultValue: "Unknown")
   String name;
 
   /// Unique identificator of the category
+  @JsonKey(required: true, disallowNullValue: true)
   final int id;
 
   /// Selected Icon for the category
-  @JsonKey(fromJson: _iconDataFromJson, toJson: _iconDataToJson)
+  @JsonKey(
+    fromJson: _iconDataFromJson,
+    toJson: _iconDataToJson,
+    defaultValue: _defaultIcon,
+  )
   IconData icon;
 
   /// The color that will be displayed with entry
-  @JsonKey(fromJson: _colorFromJson, toJson: _colorToJson)
+  @JsonKey(
+    fromJson: _colorFromJson,
+    toJson: _colorToJson,
+    defaultValue: _defaultColor,
+  )
   Color color;
 
   /// Converts the data in this instance into a Map
@@ -62,3 +80,6 @@ enum EntryType {
   /// Income
   income
 }
+
+IconData _defaultIcon() => Icons.question_mark;
+Color _defaultColor() => Colors.green;
diff --git a/lib/api/category.g.dart b/lib/api/category.g.dart
index deaf100..e2140b3 100644
--- a/lib/api/category.g.dart
+++ b/lib/api/category.g.dart
@@ -6,13 +6,23 @@ part of 'category.dart';
 // JsonSerializableGenerator
 // **************************************************************************
 
-WalletCategory _$WalletCategoryFromJson(Map<String, dynamic> json) =>
-    WalletCategory(
-      name: json['name'] as String,
-      id: (json['id'] as num).toInt(),
-      icon: _iconDataFromJson(json['icon'] as Map<String, dynamic>),
-      color: _colorFromJson((json['color'] as num).toInt()),
-    );
+WalletCategory _$WalletCategoryFromJson(Map<String, dynamic> json) {
+  $checkKeys(
+    json,
+    requiredKeys: const ['id'],
+    disallowNullValues: const ['id'],
+  );
+  return WalletCategory(
+    name: json['name'] as String? ?? 'Unknown',
+    id: (json['id'] as num).toInt(),
+    icon: json['icon'] == null
+        ? _defaultIcon()
+        : _iconDataFromJson(json['icon'] as Map<String, dynamic>),
+    color: json['color'] == null
+        ? _defaultColor()
+        : _colorFromJson((json['color'] as num).toInt()),
+  );
+}
 
 Map<String, dynamic> _$WalletCategoryToJson(WalletCategory instance) =>
     <String, dynamic>{
diff --git a/lib/api/debt_entry.dart b/lib/api/debt_entry.dart
index 9f32489..b25f28b 100644
--- a/lib/api/debt_entry.dart
+++ b/lib/api/debt_entry.dart
@@ -25,14 +25,18 @@ class DebtEntry {
   Map<String, dynamic> toJson() => _$DebtEntryToJson(this);
 
   /// Unique identifier
+  @JsonKey(required: true, disallowNullValue: true)
   final int id;
 
   /// The payed amount
+  @JsonKey(defaultValue: 0)
   int amount;
 
   /// User-friendly identifier for the transaction
+  @JsonKey(defaultValue: "Unknown")
   String name;
 
   /// List of people who payed
+  @JsonKey(defaultValue: DebtPerson.unknownPerson)
   List<DebtPerson> whoPayed;
 }
diff --git a/lib/api/debt_entry.g.dart b/lib/api/debt_entry.g.dart
index 7ec825e..e939cf1 100644
--- a/lib/api/debt_entry.g.dart
+++ b/lib/api/debt_entry.g.dart
@@ -6,14 +6,22 @@ part of 'debt_entry.dart';
 // JsonSerializableGenerator
 // **************************************************************************
 
-DebtEntry _$DebtEntryFromJson(Map<String, dynamic> json) => DebtEntry(
-      id: (json['id'] as num).toInt(),
-      amount: (json['amount'] as num).toInt(),
-      name: json['name'] as String,
-      whoPayed: (json['whoPayed'] as List<dynamic>)
-          .map((e) => DebtPerson.fromJson(e as Map<String, dynamic>))
-          .toList(),
-    );
+DebtEntry _$DebtEntryFromJson(Map<String, dynamic> json) {
+  $checkKeys(
+    json,
+    requiredKeys: const ['id'],
+    disallowNullValues: const ['id'],
+  );
+  return DebtEntry(
+    id: (json['id'] as num).toInt(),
+    amount: (json['amount'] as num?)?.toInt() ?? 0,
+    name: json['name'] as String? ?? 'Unknown',
+    whoPayed: (json['whoPayed'] as List<dynamic>?)
+            ?.map((e) => DebtPerson.fromJson(e as Map<String, dynamic>))
+            .toList() ??
+        DebtPerson.unknownPerson(),
+  );
+}
 
 Map<String, dynamic> _$DebtEntryToJson(DebtEntry instance) => <String, dynamic>{
       'id': instance.id,
diff --git a/lib/api/debt_person.dart b/lib/api/debt_person.dart
index 47531fc..d17676f 100644
--- a/lib/api/debt_person.dart
+++ b/lib/api/debt_person.dart
@@ -8,6 +8,9 @@ class DebtPerson {
   /// Represents a single person in a debt scenario
   DebtPerson({required this.id, required this.name});
 
+  /// Default [DebtPerson] instance for json_serializable
+  factory DebtPerson.unknownPerson() => DebtPerson(id: -1, name: "Unknown");
+
   /// Generates a class instance from a Map
   factory DebtPerson.fromJson(Map<String, dynamic> json) =>
       _$DebtPersonFromJson(json);
@@ -16,8 +19,10 @@ class DebtPerson {
   Map<String, dynamic> toJson() => _$DebtPersonToJson(this);
 
   /// Unique identifier
+  @JsonKey(required: true, disallowNullValue: true)
   final int id;
 
   /// Identifier that the user will see
+  @JsonKey(defaultValue: "Unknown")
   String name;
 }
diff --git a/lib/api/debt_person.g.dart b/lib/api/debt_person.g.dart
index d947448..e20c32b 100644
--- a/lib/api/debt_person.g.dart
+++ b/lib/api/debt_person.g.dart
@@ -6,10 +6,17 @@ part of 'debt_person.dart';
 // JsonSerializableGenerator
 // **************************************************************************
 
-DebtPerson _$DebtPersonFromJson(Map<String, dynamic> json) => DebtPerson(
-      id: (json['id'] as num).toInt(),
-      name: json['name'] as String,
-    );
+DebtPerson _$DebtPersonFromJson(Map<String, dynamic> json) {
+  $checkKeys(
+    json,
+    requiredKeys: const ['id'],
+    disallowNullValues: const ['id'],
+  );
+  return DebtPerson(
+    id: (json['id'] as num).toInt(),
+    name: json['name'] as String? ?? 'Unknown',
+  );
+}
 
 Map<String, dynamic> _$DebtPersonToJson(DebtPerson instance) =>
     <String, dynamic>{
diff --git a/lib/api/debt_scenario.dart b/lib/api/debt_scenario.dart
index 0ede810..e3d7120 100644
--- a/lib/api/debt_scenario.dart
+++ b/lib/api/debt_scenario.dart
@@ -23,17 +23,24 @@ class DebtScenario {
   Map<String, dynamic> toJson() => _$DebtScenarioToJson(this);
 
   /// Unique identified
+  @JsonKey(disallowNullValue: true)
   final int id;
 
   /// User-friendly identifier
+  @JsonKey(defaultValue: "Unknown")
   String name;
 
   /// Whether this scenario should be shown under archived ones
+  @JsonKey(defaultValue: false)
   bool isArchived;
 
   /// All entries
+  @JsonKey(defaultValue: [])
   List<DebtEntry> entries;
 
   /// All people
+  @JsonKey(defaultValue: _defaultPeopleList)
   List<DebtPerson> people;
 }
+
+List<DebtPerson> _defaultPeopleList() => [DebtPerson.unknownPerson()];
diff --git a/lib/api/debt_scenario.g.dart b/lib/api/debt_scenario.g.dart
index 38818cd..55b4980 100644
--- a/lib/api/debt_scenario.g.dart
+++ b/lib/api/debt_scenario.g.dart
@@ -6,19 +6,25 @@ part of 'debt_scenario.dart';
 // JsonSerializableGenerator
 // **************************************************************************
 
-DebtScenario _$DebtScenarioFromJson(Map<String, dynamic> json) => DebtScenario(
-      id: (json['id'] as num).toInt(),
-      name: json['name'] as String,
-      isArchived: json['isArchived'] as bool,
-      entries: (json['entries'] as List<dynamic>?)
-              ?.map((e) => DebtEntry.fromJson(e as Map<String, dynamic>))
-              .toList() ??
-          const [],
-      people: (json['people'] as List<dynamic>?)
-              ?.map((e) => DebtPerson.fromJson(e as Map<String, dynamic>))
-              .toList() ??
-          const [],
-    );
+DebtScenario _$DebtScenarioFromJson(Map<String, dynamic> json) {
+  $checkKeys(
+    json,
+    disallowNullValues: const ['id'],
+  );
+  return DebtScenario(
+    id: (json['id'] as num).toInt(),
+    name: json['name'] as String? ?? 'Unknown',
+    isArchived: json['isArchived'] as bool? ?? false,
+    entries: (json['entries'] as List<dynamic>?)
+            ?.map((e) => DebtEntry.fromJson(e as Map<String, dynamic>))
+            .toList() ??
+        [],
+    people: (json['people'] as List<dynamic>?)
+            ?.map((e) => DebtPerson.fromJson(e as Map<String, dynamic>))
+            .toList() ??
+        _defaultPeopleList(),
+  );
+}
 
 Map<String, dynamic> _$DebtScenarioToJson(DebtScenario instance) =>
     <String, dynamic>{
diff --git a/lib/api/entry_data.dart b/lib/api/entry_data.dart
index 498e07e..d59f532 100644
--- a/lib/api/entry_data.dart
+++ b/lib/api/entry_data.dart
@@ -15,13 +15,19 @@ class EntryData {
   factory EntryData.fromJson(Map<String, dynamic> json) =>
       _$EntryDataFromJson(json);
 
+  /// [EntryData] instance used as a default value for json_serializable
+  factory EntryData.unknown() => EntryData(name: "Unknown", amount: 0);
+
   /// Name of entry
+  @JsonKey(defaultValue: "Unknown")
   String name;
 
   /// Optional description, default is empty
+  @JsonKey(defaultValue: "")
   String description;
 
   /// Amount for entry
+  @JsonKey(defaultValue: 0)
   double amount;
 
   /// Converts the data in this instance into a Map
diff --git a/lib/api/entry_data.g.dart b/lib/api/entry_data.g.dart
index 48a4faa..1ccbf8d 100644
--- a/lib/api/entry_data.g.dart
+++ b/lib/api/entry_data.g.dart
@@ -7,9 +7,9 @@ part of 'entry_data.dart';
 // **************************************************************************
 
 EntryData _$EntryDataFromJson(Map<String, dynamic> json) => EntryData(
-      name: json['name'] as String,
-      amount: (json['amount'] as num).toDouble(),
-      description: json['description'] as String? ?? "",
+      name: json['name'] as String? ?? 'Unknown',
+      amount: (json['amount'] as num?)?.toDouble() ?? 0,
+      description: json['description'] as String? ?? '',
     );
 
 Map<String, dynamic> _$EntryDataToJson(EntryData instance) => <String, dynamic>{
diff --git a/lib/api/recurring_entry.dart b/lib/api/recurring_entry.dart
index fc57bc0..72b78f9 100644
--- a/lib/api/recurring_entry.dart
+++ b/lib/api/recurring_entry.dart
@@ -33,12 +33,15 @@ class RecurringWalletEntry extends WalletSingleEntry {
   Map<String, dynamic> toJson() => _$RecurringWalletEntryToJson(this);
 
   /// Last date the recurring entry was added into the single entry list
+  @JsonKey(defaultValue: DateTime.now)
   DateTime lastRunDate;
 
   /// After how many {recurType} should the entry recur
+  @JsonKey(defaultValue: 1)
   int repeatAfter;
 
   /// What type of recurrence should happen
+  @JsonKey(defaultValue: RecurType.month)
   RecurType recurType;
 }
 
diff --git a/lib/api/recurring_entry.g.dart b/lib/api/recurring_entry.g.dart
index a8abb86..4812c59 100644
--- a/lib/api/recurring_entry.g.dart
+++ b/lib/api/recurring_entry.g.dart
@@ -6,19 +6,33 @@ part of 'recurring_entry.dart';
 // JsonSerializableGenerator
 // **************************************************************************
 
-RecurringWalletEntry _$RecurringWalletEntryFromJson(
-        Map<String, dynamic> json) =>
-    RecurringWalletEntry(
-      data: EntryData.fromJson(json['data'] as Map<String, dynamic>),
-      type: $enumDecode(_$EntryTypeEnumMap, json['type']),
-      date: DateTime.parse(json['date'] as String),
-      category:
-          WalletCategory.fromJson(json['category'] as Map<String, dynamic>),
-      id: (json['id'] as num).toInt(),
-      lastRunDate: DateTime.parse(json['lastRunDate'] as String),
-      recurType: $enumDecode(_$RecurTypeEnumMap, json['recurType']),
-      repeatAfter: (json['repeatAfter'] as num?)?.toInt() ?? 1,
-    );
+RecurringWalletEntry _$RecurringWalletEntryFromJson(Map<String, dynamic> json) {
+  $checkKeys(
+    json,
+    requiredKeys: const ['id'],
+    disallowNullValues: const ['id'],
+  );
+  return RecurringWalletEntry(
+    data: json['data'] == null
+        ? EntryData.unknown()
+        : EntryData.fromJson(json['data'] as Map<String, dynamic>),
+    type: $enumDecodeNullable(_$EntryTypeEnumMap, json['type']) ??
+        EntryType.expense,
+    date: json['date'] == null
+        ? DateTime.now()
+        : DateTime.parse(json['date'] as String),
+    category: json['category'] == null
+        ? WalletCategory.unknown()
+        : WalletCategory.fromJson(json['category'] as Map<String, dynamic>),
+    id: (json['id'] as num).toInt(),
+    lastRunDate: json['lastRunDate'] == null
+        ? DateTime.now()
+        : DateTime.parse(json['lastRunDate'] as String),
+    recurType: $enumDecodeNullable(_$RecurTypeEnumMap, json['recurType']) ??
+        RecurType.month,
+    repeatAfter: (json['repeatAfter'] as num?)?.toInt() ?? 1,
+  );
+}
 
 Map<String, dynamic> _$RecurringWalletEntryToJson(
         RecurringWalletEntry instance) =>
diff --git a/lib/api/wallet.dart b/lib/api/wallet.dart
index df9f81e..b8cd91b 100644
--- a/lib/api/wallet.dart
+++ b/lib/api/wallet.dart
@@ -38,24 +38,32 @@ class Wallet {
   factory Wallet.fromJson(Map<String, dynamic> json) => _$WalletFromJson(json);
 
   /// A list of all [RecurringWalletEntry]s
+  @JsonKey(defaultValue: [])
   final List<RecurringWalletEntry> recurringEntries;
 
   /// Name of the wallet
+  @JsonKey(defaultValue: "Unknown")
   final String name;
 
   /// A list of available categories
+  @JsonKey(defaultValue: _defaultWalletCategory)
   final List<WalletCategory> categories;
 
   /// List of saved entries
+  @JsonKey(defaultValue: [])
   final List<WalletSingleEntry> entries;
 
   /// The starting balance of the wallet
   ///
   /// Used to calculate current balance
+  @JsonKey(defaultValue: 0)
   double starterBalance;
 
   /// Selected currency
-  @JsonKey(fromJson: _currencyFromJson)
+  @JsonKey(
+    fromJson: _currencyFromJson,
+    defaultValue: _defaultCurrency,
+  )
   final Currency currency;
 
   /// Converts the data in this instance into a Map
@@ -281,3 +289,20 @@ class Wallet {
     WalletManager.saveWallet(this);
   }
 }
+
+List<WalletCategory> _defaultWalletCategory() => [WalletCategory.unknown()];
+Currency _defaultCurrency() => Currency.from(
+      json: {
+        "code": "USD",
+        "name": "United States Dollar",
+        "symbol": r"$",
+        "flag": "USD",
+        "decimal_digits": 2,
+        "number": 840,
+        "name_plural": "US dollars",
+        "thousands_separator": ",",
+        "decimal_separator": ".",
+        "space_between_amount_and_symbol": false,
+        "symbol_on_left": true,
+      },
+    );
diff --git a/lib/api/wallet.g.dart b/lib/api/wallet.g.dart
index 561b831..277d410 100644
--- a/lib/api/wallet.g.dart
+++ b/lib/api/wallet.g.dart
@@ -7,22 +7,24 @@ part of 'wallet.dart';
 // **************************************************************************
 
 Wallet _$WalletFromJson(Map<String, dynamic> json) => Wallet(
-      name: json['name'] as String,
-      currency: _currencyFromJson(json['currency'] as Map<String, dynamic>),
+      name: json['name'] as String? ?? 'Unknown',
+      currency: json['currency'] == null
+          ? _defaultCurrency()
+          : _currencyFromJson(json['currency'] as Map<String, dynamic>),
       categories: (json['categories'] as List<dynamic>?)
               ?.map((e) => WalletCategory.fromJson(e as Map<String, dynamic>))
               .toList() ??
-          const [],
+          _defaultWalletCategory(),
       entries: (json['entries'] as List<dynamic>?)
               ?.map(
                   (e) => WalletSingleEntry.fromJson(e as Map<String, dynamic>))
               .toList() ??
-          const [],
+          [],
       recurringEntries: (json['recurringEntries'] as List<dynamic>?)
               ?.map((e) =>
                   RecurringWalletEntry.fromJson(e as Map<String, dynamic>))
               .toList() ??
-          const [],
+          [],
       starterBalance: (json['starterBalance'] as num?)?.toDouble() ?? 0,
     );
 
diff --git a/lib/api/wallet_entry.dart b/lib/api/wallet_entry.dart
index 77aed05..10d586e 100644
--- a/lib/api/wallet_entry.dart
+++ b/lib/api/wallet_entry.dart
@@ -26,19 +26,24 @@ class WalletSingleEntry {
       _$WalletSingleEntryFromJson(json);
 
   /// Expense or income
+  @JsonKey(defaultValue: EntryType.expense)
   EntryType type;
 
   /// Actual entry data
+  @JsonKey(defaultValue: EntryData.unknown)
   EntryData data;
 
   /// Date of entry creation
+  @JsonKey(defaultValue: DateTime.now)
   DateTime date;
 
   /// Selected category
+  @JsonKey(defaultValue: WalletCategory.unknown)
   WalletCategory category;
 
   /// Unique entry ID
-  int id;
+  @JsonKey(required: true, disallowNullValue: true)
+  final int id;
 
   /// Converts the data in this instance into a Map
   Map<String, dynamic> toJson() => _$WalletSingleEntryToJson(this);
diff --git a/lib/api/wallet_entry.g.dart b/lib/api/wallet_entry.g.dart
index 4ce4cff..067bc4a 100644
--- a/lib/api/wallet_entry.g.dart
+++ b/lib/api/wallet_entry.g.dart
@@ -6,15 +6,27 @@ part of 'wallet_entry.dart';
 // JsonSerializableGenerator
 // **************************************************************************
 
-WalletSingleEntry _$WalletSingleEntryFromJson(Map<String, dynamic> json) =>
-    WalletSingleEntry(
-      data: EntryData.fromJson(json['data'] as Map<String, dynamic>),
-      type: $enumDecode(_$EntryTypeEnumMap, json['type']),
-      date: DateTime.parse(json['date'] as String),
-      category:
-          WalletCategory.fromJson(json['category'] as Map<String, dynamic>),
-      id: (json['id'] as num).toInt(),
-    );
+WalletSingleEntry _$WalletSingleEntryFromJson(Map<String, dynamic> json) {
+  $checkKeys(
+    json,
+    requiredKeys: const ['id'],
+    disallowNullValues: const ['id'],
+  );
+  return WalletSingleEntry(
+    data: json['data'] == null
+        ? EntryData.unknown()
+        : EntryData.fromJson(json['data'] as Map<String, dynamic>),
+    type: $enumDecodeNullable(_$EntryTypeEnumMap, json['type']) ??
+        EntryType.expense,
+    date: json['date'] == null
+        ? DateTime.now()
+        : DateTime.parse(json['date'] as String),
+    category: json['category'] == null
+        ? WalletCategory.unknown()
+        : WalletCategory.fromJson(json['category'] as Map<String, dynamic>),
+    id: (json['id'] as num).toInt(),
+  );
+}
 
 Map<String, dynamic> _$WalletSingleEntryToJson(WalletSingleEntry instance) =>
     <String, dynamic>{