diff --git a/src/bill/calculator.py b/src/bill/calculator.py
index b02117c..90bdbb0 100644
--- a/src/bill/calculator.py
+++ b/src/bill/calculator.py
@@ -242,7 +242,14 @@ def get_shares_spreadsheet(self):
         current_row += 1
 
         for extra in self.extras.items:
-            row_data = [extra.name, extra.price]
+            percentage = (extra.price / subtotal) * 100
+            if percentage == int(percentage):
+                formatted_percentage = f"{int(percentage)}%"
+            else:
+                formatted_percentage = f"{percentage:.2f}%"
+            extra_name_with_percentage = f"{extra.name} ({formatted_percentage})"
+
+            row_data = [extra_name_with_percentage, extra.price]
             for col_idx in range(person_count):
                 col_letter = chr(ord("C") + col_idx)
                 formula = (
diff --git a/tests/test_calculator.py b/tests/test_calculator.py
index 375763e..ab12fd9 100644
--- a/tests/test_calculator.py
+++ b/tests/test_calculator.py
@@ -267,7 +267,7 @@ def test_spreadsheet(calculator, sample_persons):
     assert worksheet[f"F{subtotal_row}"].value == "=SUM(C18:E18)"
 
     service_charge_row = 19
-    assert worksheet[f"A{service_charge_row}"].value == SERVICE_CHARGE
+    assert worksheet[f"A{service_charge_row}"].value == "Service Charge (20%)"
     service_charge = subtotal * SERVICE_CHARGE_RATIO
     assert worksheet[f"B{service_charge_row}"].value == service_charge
 
@@ -289,7 +289,7 @@ def test_spreadsheet(calculator, sample_persons):
     )
 
     tax_row = 20
-    assert worksheet[f"A{tax_row}"].value == TAX
+    assert worksheet[f"A{tax_row}"].value == "Tax (10.35%)"
     tax = subtotal * TAX_RATIO
     assert worksheet[f"B{tax_row}"].value == tax