diff --git a/changelog.d/fix-apply-uprating-redundant-copy.changed.md b/changelog.d/fix-apply-uprating-redundant-copy.changed.md
new file mode 100644
index 000000000..3adbe304f
--- /dev/null
+++ b/changelog.d/fix-apply-uprating-redundant-copy.changed.md
@@ -0,0 +1 @@
+Added `copy` parameter to `apply_uprating` (default `True`); `extend_single_year_dataset` now passes `copy=False` to skip the redundant deep copy of the multi-year dataset since each year is already copied individually.
diff --git a/policyengine_uk/data/economic_assumptions.py b/policyengine_uk/data/economic_assumptions.py
index 9c6d84946..1b33994f9 100644
--- a/policyengine_uk/data/economic_assumptions.py
+++ b/policyengine_uk/data/economic_assumptions.py
@@ -48,21 +48,23 @@ def extend_single_year_dataset(
     return apply_uprating(
         multi_year_dataset,
         tax_benefit_system_parameters=tax_benefit_system_parameters,
+        copy=False,
     )
 
 
 def apply_uprating(
     dataset: UKMultiYearDataset,
     tax_benefit_system_parameters: ParameterNode = None,
+    copy: bool = True,
 ):
     from policyengine_uk.system import system
 
-    # Apply uprating to the dataset.
-    dataset = dataset.copy()
-
     if not isinstance(dataset, UKMultiYearDataset):
         raise TypeError("dataset must be of type UKMultiYearDataset.")
 
+    if copy:
+        dataset = dataset.copy()
+
     for year in dataset.datasets.keys():
         if year == min(dataset.datasets.keys()):
             continue  # Don't uprate the first year