diff --git a/app/main.py b/app/main.py
index 1609f1c..58e02d7 100644
--- a/app/main.py
+++ b/app/main.py
@@ -11,7 +11,7 @@ from .models import User, Vehicle, FuelEntry, CompanySettings, AppSetting, Orlen
 from .services import calculate_costs, fetch_orlen_price, fetch_orlen_range, invoice_period, fetch_ure_stations, aggregate_ure_companies, POLISH_REGIONS
 from .station_catalog import sync_station_catalog
 from . import THEMES
-from .vat import entry_vat_rate, freeze_vat_action, global_vat_override, save_global_vat_override
+from .vat import effective_vat_rate, entry_vat_rate, freeze_vat_action, global_vat_override, save_global_vat_override
 from .settlement import calculate as calculate_snapshot_settlement, freeze as freeze_settlement
 from .orlen_sync import sync_orlen_prices
 
diff --git a/tests/test_app.py b/tests/test_app.py
index 0cd4d2a..b04e18a 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -505,3 +505,48 @@ def test_orlen_page_has_incremental_and_full_refresh_controls(tmp_path):
     assert 'Pobierz nowe dane' in html
     assert 'id="orlen-full-sync-btn"' in html
     assert 'Pobierz cały wybrany rok ponownie' in html
+
+
+def test_orlen_period_comparison_adds_effective_vat_for_each_date(tmp_path):
+    from datetime import date
+    from decimal import Decimal
+    from app.extensions import db
+    from app.models import AppSetting, OrlenPrice
+
+    app = make_app(tmp_path, "orlen-period-vat.db")
+    client = app.test_client()
+    client.post('/login', data={'email': 'admin@example.com', 'password': 'admin123!'})
+
+    with app.app_context():
+        for key, value in {
+            'global_vat_override_enabled': '1',
+            'global_vat_override_name': 'Czasowa stawka',
+            'global_vat_override_rate': '8',
+            'global_vat_override_start': '2026-07-01',
+            'global_vat_override_end': '2026-07-31',
+        }.items():
+            db.session.merge(AppSetting(key=key, value=value))
+        db.session.add_all([
+            OrlenPrice(
+                fuel_type='PB95', effective_date=date(2026, 7, 15),
+                price_per_liter=Decimal('100.0000'), raw_value=Decimal('100000'),
+                region='', product_name='PB95', source='test',
+            ),
+            OrlenPrice(
+                fuel_type='PB95', effective_date=date(2026, 8, 1),
+                price_per_liter=Decimal('100.0000'), raw_value=Decimal('100000'),
+                region='', product_name='PB95', source='test',
+            ),
+        ])
+        db.session.commit()
+
+    response = client.get(
+        '/orlen?mode=compare&comparison_type=periods&compare_fuel=PB95&gross=1'
+        '&period_a_from=2026-07-01&period_a_to=2026-07-31'
+        '&period_b_from=2026-08-01&period_b_to=2026-08-31'
+    )
+
+    assert response.status_code == 200
+    html = response.get_data(as_text=True)
+    assert '108.0000 zł/l' in html
+    assert '123.0000 zł/l' in html