diff --git a/android/app/build.gradle.kts b/android/app/build.gradle.kts
index d47e69a..82cccf6 100644
--- a/android/app/build.gradle.kts
+++ b/android/app/build.gradle.kts
@@ -13,6 +13,7 @@ android {
     compileOptions {
         sourceCompatibility = JavaVersion.VERSION_17
         targetCompatibility = JavaVersion.VERSION_17
+        isCoreLibraryDesugaringEnabled = true
     }
 
     kotlinOptions {
@@ -39,6 +40,10 @@ android {
     }
 }
 
+dependencies {
+    coreLibraryDesugaring("com.android.tools:desugar_jdk_libs:2.1.4")
+}
+
 flutter {
     source = "../.."
 }
diff --git a/lib/state/rent_controller.dart b/lib/state/rent_controller.dart
index ed827cd..18de39f 100644
--- a/lib/state/rent_controller.dart
+++ b/lib/state/rent_controller.dart
@@ -41,6 +41,7 @@ class RentController extends ChangeNotifier {
   RentController({
     StorageService? storageService,
     ForexRateApiService? exchangeService,
+    NotificationService? notificationService,
   }) : _storageService = storageService ?? StorageService(),
        _exchangeService =
            exchangeService ??
@@ -48,7 +49,8 @@ class RentController extends ChangeNotifier {
              httpClient: http.Client(),
              apiKey: _exchangeRateApiKeyFromEnv(),
            ) {
-    _notificationService = NotificationService(_onNotificationAction);
+    _notificationService =
+        notificationService ?? NotificationService(_onNotificationAction);
   }
 
   static String _exchangeRateApiKeyFromEnv() {
diff --git a/test/backup_restore_compatibility_test.dart b/test/backup_restore_compatibility_test.dart
new file mode 100644
index 0000000..2c49dfb
--- /dev/null
+++ b/test/backup_restore_compatibility_test.dart
@@ -0,0 +1,202 @@
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:http/http.dart' as http;
+import 'package:rental_income_tracker/models/app_settings.dart';
+import 'package:rental_income_tracker/models/monthly_rent_record.dart';
+import 'package:rental_income_tracker/services/notification_service.dart';
+import 'package:rental_income_tracker/services/open_exchange_service.dart';
+import 'package:rental_income_tracker/services/storage_service.dart';
+import 'package:rental_income_tracker/state/rent_controller.dart';
+
+class _FakeStorageService extends StorageService {
+  AppSettings _settings = AppSettings.defaults();
+  Map<String, MonthlyRentRecord> _records = <String, MonthlyRentRecord>{};
+
+  @override
+  Future<AppSettings> loadSettings() async => _settings;
+
+  @override
+  Future<void> saveSettings(AppSettings settings) async {
+    _settings = settings;
+  }
+
+  @override
+  Future<Map<String, MonthlyRentRecord>> loadRecords() async =>
+      Map<String, MonthlyRentRecord>.from(_records);
+
+  @override
+  Future<void> saveRecords(Map<String, MonthlyRentRecord> records) async {
+    _records = Map<String, MonthlyRentRecord>.from(records);
+  }
+}
+
+class _FakeExchangeService extends ForexRateApiService {
+  _FakeExchangeService({required this.quote})
+    : super(httpClient: http.Client(), apiKey: 'test-key');
+
+  final double quote;
+
+  @override
+  Future<ForexConversionResult> convertUsdToSek({
+    required DateTime estDate,
+    required double amount,
+  }) async {
+    return ForexConversionResult(quote: quote, result: quote * amount);
+  }
+}
+
+class _FakeNotificationService extends NotificationService {
+  _FakeNotificationService() : super((_) async {});
+
+  @override
+  Future<void> initialize() async {}
+
+  @override
+  Future<void> processPendingActions() async {}
+
+  @override
+  Future<void> scheduleForMonth({
+    required int year,
+    required int month,
+    required int quietHourStart,
+    required int fallbackHour,
+  }) async {}
+
+  @override
+  Future<void> cancelForMonth(int year, int month) async {}
+
+  @override
+  Future<void> cancelAll() async {}
+}
+
+void main() {
+  group('backup/import compatibility', () {
+    test(
+      'round-trips current backup format through export and import',
+      () async {
+        final sourceStorage = _FakeStorageService();
+        final sourceController = RentController(
+          storageService: sourceStorage,
+          exchangeService: _FakeExchangeService(quote: 10.5),
+          notificationService: _FakeNotificationService(),
+        );
+
+        await sourceController.updateRentUsd(2450);
+        await sourceController.setMonthStatusManually(
+          year: 2025,
+          month: 1,
+          status: PaymentStatus.onTime,
+          paidUsd: 2000,
+        );
+        await sourceController.setMonthStatusManually(
+          year: 2025,
+          month: 2,
+          status: PaymentStatus.late,
+          paidUsd: 1800,
+        );
+
+        final tempDir = await Directory.systemTemp.createTemp('backup_test_');
+        addTearDown(() async {
+          if (await tempDir.exists()) {
+            await tempDir.delete(recursive: true);
+          }
+        });
+
+        final backupPath = await sourceController.exportBackupToDirectory(
+          tempDir.path,
+        );
+
+        final targetStorage = _FakeStorageService();
+        final targetController = RentController(
+          storageService: targetStorage,
+          exchangeService: _FakeExchangeService(quote: 99),
+          notificationService: _FakeNotificationService(),
+        );
+
+        await targetController.importBackupFromFile(backupPath);
+
+        expect(targetController.settings.rentUsd, 2450);
+
+        targetController.selectYear(2025);
+        final rows = targetController.buildRowsForSelectedYear();
+        final january = rows.firstWhere((row) => row.month == 1);
+        final february = rows.firstWhere((row) => row.month == 2);
+
+        expect(january.status, PaymentStatus.onTime);
+        expect(january.usdAmount, 2000);
+        expect(january.sekAmount, 21000);
+        expect(january.effectiveUsdToSekRate, 10.5);
+
+        expect(february.status, PaymentStatus.late);
+        expect(february.usdAmount, 1800);
+        expect(february.sekAmount, 18900);
+        expect(february.effectiveUsdToSekRate, 10.5);
+
+        final persistedSettings = await targetStorage.loadSettings();
+        final persistedRecords = await targetStorage.loadRecords();
+        expect(persistedSettings.rentUsd, 2450);
+        expect(
+          persistedRecords.keys,
+          containsAll(<String>['2025-01', '2025-02']),
+        );
+      },
+    );
+
+    test(
+      'imports legacy export payloads with missing optional fields',
+      () async {
+        final tempDir = await Directory.systemTemp.createTemp('backup_legacy_');
+        addTearDown(() async {
+          if (await tempDir.exists()) {
+            await tempDir.delete(recursive: true);
+          }
+        });
+
+        final legacyFile = File('${tempDir.path}/legacy_export.json');
+        await legacyFile.writeAsString('''
+{
+  "exportedAtUtc": "2026-03-20T10:00:00.000Z",
+  "settings": {
+    "rentUsd": 1995.0,
+    "occupied": true
+  },
+  "records": [
+    {
+      "year": 2024,
+      "month": 12,
+      "usdAmount": 1995.0,
+      "sekAmount": 21446.25,
+      "usdToSekRate": 10.75,
+      "paidAtUtc": "2024-12-02T12:00:00.000Z",
+      "onTime": false
+    }
+  ]
+}
+''');
+
+        final controller = RentController(
+          storageService: _FakeStorageService(),
+          exchangeService: _FakeExchangeService(quote: 1),
+          notificationService: _FakeNotificationService(),
+        );
+
+        await controller.importBackupFromFile(legacyFile.path);
+
+        expect(controller.settings.rentUsd, 1995.0);
+        expect(controller.settings.localFallbackHour, 9);
+        expect(controller.settings.localQuietHourStart, 23);
+
+        controller.selectYear(2024);
+        final december = controller.buildRowsForSelectedYear().firstWhere(
+          (row) => row.month == 12,
+        );
+
+        expect(december.status, PaymentStatus.late);
+        expect(december.usdAmount, 1995.0);
+        expect(december.sekAmount, 21446.25);
+        expect(december.effectiveUsdToSekRate, 10.75);
+      },
+    );
+  });
+}