diff --git a/recommendations/optimiser/optimiser_functions.py b/recommendations/optimiser/optimiser_functions.py
index 95309a19..5175c6b6 100644
--- a/recommendations/optimiser/optimiser_functions.py
+++ b/recommendations/optimiser/optimiser_functions.py
@@ -90,7 +90,10 @@ def prepare_input_measures(property_recommendations, goal, needs_ventilation, fu
                     if rec["measure_type"] in assumptions.measures_needing_ventilation and needs_ventilation
                     else rec["total"]
                 )
-            total = 0 if total < 0 else total
+
+            # If the innovation uplift being removed make this negative, we keep the total so we can re-engineer
+            # the original cost
+            non_negative_total = 0 if total < 0 else total
             gain = (
                 rec[goal_key] + ventilation_recommendation[goal_key]
                 if rec["measure_type"] in assumptions.measures_needing_ventilation and needs_ventilation
@@ -105,8 +108,9 @@ def prepare_input_measures(property_recommendations, goal, needs_ventilation, fu
             # We also include the innovation uplift
             to_append.append(
                 {
-                    "id": rec["recommendation_id"], "cost": total, "gain": gain, "type": rec_type,
+                    "id": rec["recommendation_id"], "cost": non_negative_total, "gain": gain, "type": rec_type,
                     "innovation_uplift": rec["innovation_uplift"] if funding else 0,
+                    "cost_minus_uplift": total
                 }
             )
 
diff --git a/recommendations/tests/test_optimisers.py b/recommendations/tests/test_optimisers.py
index 07b42882..252ad675 100644
--- a/recommendations/tests/test_optimisers.py
+++ b/recommendations/tests/test_optimisers.py
@@ -9,6 +9,9 @@ from recommendations.optimiser.CostOptimiser import CostOptimiser
 from recommendations.optimiser.GainOptimiser import GainOptimiser
 from backend.Funding import Funding
 
+# measures we DO NOT treat as fundable in the ECO4 'funded' pass
+_ECO4_EXCLUDE_TYPES = {"secondary_heating"}
+
 project_scores_matrix = pd.read_csv("/Users/khalimconn-kowlessar/Downloads/ECO4 Full Project Scores Matrix.csv")
 partial_project_scores_matrix = pd.read_csv("backend/tests/test_data/ECO4_Partial_Project_Scores_Matrix_v6.csv")
 partial_project_scores_matrix.columns = ['Measure category', 'Measure_Type', 'Pre_Main_Heating_Source',
@@ -460,30 +463,6 @@ input_measures = optimiser_functions.prepare_input_measures(
     measures_to_optimise, "Increasing EPC", needs_ventilation, True
 )
 
-# ---- rule definitions you can tweak -------------------------------------
-
-HEATING_TYPES = {"air_source_heat_pump", "high_heat_retention_storage_heater", "solar_pv"}
-MIN_INSULATION_OR = [{"loft_insulation"}, {"cavity_wall_insulation"}]  # extend if needed
-
-# “Funding paths”: each is a list of elements; each element is:
-#  - {"OR": {"types": {..}}} means choose one option from any group whose type is in that set
-#  - {"AND": [{"types": {..}}, {"types": {..}}]} means choose one from each of those
-FUNDING_PATHS = [
-    # Path A: IWI OR EWI
-    [
-        {
-            "OR": {
-                "types": {"internal_wall_insulation", "external_wall_insulation"}
-            }
-        }
-    ],
-    # Path B: Solar PV AND HHRSH
-    [{"AND": [{"types": {"solar_pv"}}, {"types": {"high_heat_retention_storage_heater"}}]}],
-    # Path C: ASHP alone (may still trigger min insulation rule below)
-    [{"OR": {"types": {"air_source_heat_pump"}}}],
-    #
-]
-
 
 def _find_measure(input_measures, measure_type):
     for measures in input_measures:
@@ -695,8 +674,56 @@ def make_funding_paths(p, input_measures, tenure):
 # Run inputs:
 target_gain = 18.5
 
-from itertools import product
-import math
+
+def _path_scheme(path_spec):
+    """
+    Infer scheme from any 'reference' tag in the path.
+    Defaults to 'eco4' if not specified.
+    """
+    for elem in path_spec or []:
+        ref = elem.get("reference")
+        if isinstance(ref, str):
+            if ref.endswith(":gbis"):
+                return "gbis"
+            if ref.endswith(":eco4"):
+                return "eco4"
+    return "eco4"
+
+
+def _filter_fundable_subgroups(groups, scheme):
+    """
+    Keep only options eligible for the funded pass of the given scheme.
+    - ECO4: drop excluded types (e.g., secondary_heating)
+    - GBIS: funded pass is the GBIS fixed measure only, so return empty sub-groups
+    """
+    if scheme == "gbis":
+        return []  # we won't optimise 'the rest' under GBIS here
+
+    # ECO4 case
+    filtered = []
+    for grp in groups:
+        kept = [opt for opt in grp
+                if not any(ex in opt["type"] for ex in _ECO4_EXCLUDE_TYPES)]
+        if kept:
+            filtered.append(kept)
+    return filtered
+
+
+def _sum_cost_gain_with_scheme(items, scheme):
+    """
+    Sum cost/gain of fixed items, adjusting for scheme rules.
+    - GBIS: strip innovation uplift from GBIS-funded fixed measures only.
+    """
+    total_cost = 0.0
+    total_gain = 0.0
+    for it in items:
+        cost = float(it["cost"])
+        if scheme == "gbis":
+            # innovation uplifts are not paid under GBIS
+            cost -= float(it.get("innovation_uplift", 0.0))
+        total_cost += cost
+        total_gain += float(it["gain"])
+    return total_cost, total_gain
 
 
 def violates_min_insulation(fixed):
@@ -740,11 +767,6 @@ def optimise_with_funding_paths(input_measures, budget=None, target_gain=None, s
 
     solutions = []
     for path_spec in funding_paths:
-        # TODO: If the path spec is GBIS, need to handle this differently. There is no funding associated
-        #       with the other measures we're optimising. Instead, we fix the GBIS measure (which is funded)
-        #       and then run the optimiser on the remaining measures which are NOT funded. The key change is all
-        #       measures in input_measures right now have costs adjusted with innovation uplift, which we don't want
-        #       to apply to the GBIS measures. So we need to strip the innovation uplift from the GBIS measures
         # 1) expand fixed selections for this path
         fixed_selections = expand_funding_path(input_measures, path_spec) if path_spec else [[]]
         if not fixed_selections:
@@ -758,13 +780,26 @@ def optimise_with_funding_paths(input_measures, budget=None, target_gain=None, s
                 logger.error("Skipping fixed selection due to minimum insulation violation: %s", fixed)
                 continue
 
+            scheme = _path_scheme(path_spec)
+
             # 3) compute fixed cost/gain, and strip those groups from subproblem
             fixed_items = [opt for (_, _, opt) in fixed]
             fixed_ids = [opt['id'] for opt in fixed_items]
             fixed_cost, fixed_gain = sum_cost_gain(fixed_items)
             fixed_groups = {gi for (gi, _, _) in fixed}
 
-            sub_measures = [grp for gi, grp in enumerate(input_measures) if gi not in fixed_groups]
+            sub_measures = deepcopy([grp for gi, grp in enumerate(input_measures) if gi not in fixed_groups])
+
+            if scheme == "gbis":
+                # Then for the sub-measures, we need to strip the innovation uplift from the GBIS fixed measures. We
+                # do this by adding innovation back onto the cost
+                for grp in sub_measures:
+                    for opt in grp:
+                        opt["cost"] = opt["cost_minus_uplift"] + opt.get("innovation_uplift", 0.0)
+
+            if scheme == "eco4":
+                # Need to strip out any measure types that are not eligible for ECO4 funding (e.g. secondary heating)
+                raise ValueError()
 
             # 4) run your existing optimiser for the remaining groups
             # If we have a budget, we need to ensure the subproblem respects it so we remove the fixed cost (which