diff --git a/backend/app/db/models/portfolio.py b/backend/app/db/models/portfolio.py
index 452c8d36..58aa2535 100644
--- a/backend/app/db/models/portfolio.py
+++ b/backend/app/db/models/portfolio.py
@@ -18,6 +18,11 @@ from backend.app.db.models.users import UserModel  # noqa
 from backend.app.db.models.materials import MaterialType
 from datatypes.epc.domain.epc import Epc
 
+# PortfolioGoal moved to the domain layer (ADR-0017 amendment). Re-exported here
+# so the existing `from backend.app.db.models.portfolio import PortfolioGoal`
+# callers keep working.
+from domain.modelling.portfolio_goal import PortfolioGoal  # noqa: F401
+
 
 class PortfolioStatus(enum.Enum):
     SCOPING = "scoping"
@@ -32,14 +37,6 @@ class PortfolioStatus(enum.Enum):
     NEEDS_REVIEW = "needs review"
 
 
-class PortfolioGoal(enum.Enum):  # TODO: Move to domain?
-    VALUATION_IMPROVEMENT = "Valuation Improvement"
-    INCREASING_EPC = "Increasing EPC"
-    REDUCING_CO2_EMISSIONS = "Reducing CO2 emissions"
-    ENERGY_SAVINGS = "Energy Savings"
-    NONE = "None"
-
-
 class Portfolio(Base):
     __tablename__ = "portfolio"
     id = Column(Integer, primary_key=True, autoincrement=True)
diff --git a/domain/modelling/portfolio_goal.py b/domain/modelling/portfolio_goal.py
new file mode 100644
index 00000000..9785fd2e
--- /dev/null
+++ b/domain/modelling/portfolio_goal.py
@@ -0,0 +1,23 @@
+"""PortfolioGoal — the retrofit objective a Scenario is scored against.
+
+Domain vocabulary (ubiquitous language): the goal a user sets for a Scenario —
+raise the EPC band, cut CO₂, cut energy, or improve valuation. The enum
+*values* are the canonical strings stored in the live ``scenario.goal`` /
+``portfolio.goal`` columns and used by the front end; the Modelling stage's
+Optimiser branches on them (#1160).
+
+Lives in ``domain/`` (not ``backend/``) so the domain, persistence
+(``infrastructure/postgres/modelling``) and legacy app layers share one
+definition — co-located with ``scenario.py``, which carries the goal. See
+CONTEXT.md.
+"""
+
+import enum
+
+
+class PortfolioGoal(enum.Enum):
+    VALUATION_IMPROVEMENT = "Valuation Improvement"
+    INCREASING_EPC = "Increasing EPC"
+    REDUCING_CO2_EMISSIONS = "Reducing CO2 emissions"
+    ENERGY_SAVINGS = "Energy Savings"
+    NONE = "None"