diff --git a/app/models/variant_override.rb b/app/models/variant_override.rb
index 89d2fdcd13..d28bb2771f 100644
--- a/app/models/variant_override.rb
+++ b/app/models/variant_override.rb
@@ -10,6 +10,8 @@ class VariantOverride < ActiveRecord::Base
   # Default stock can be nil, indicating stock should not be reset or zero, meaning reset to zero. Need to ensure this can be set by the user.
   validates :default_stock, numericality: { greater_than_or_equal_to: 0 }, allow_nil: true
 
+  before_validation :require_compatible_on_demand_and_count_on_hand
+
   after_save :refresh_products_cache_from_save
   after_destroy :refresh_products_cache_from_destroy
 
@@ -104,4 +106,38 @@ class VariantOverride < ActiveRecord::Base
   def refresh_products_cache_from_destroy
     OpenFoodNetwork::ProductsCache.variant_override_destroyed self
   end
+
+  def require_compatible_on_demand_and_count_on_hand
+    disallow_count_on_hand_if_using_producer_stock_settings
+    disallow_count_on_hand_if_on_demand
+    require_count_on_hand_if_limited_stock
+  end
+
+  def disallow_count_on_hand_if_using_producer_stock_settings
+    return unless on_demand.nil? && count_on_hand.present?
+
+    error_message = I18n.t("using_producer_stock_settings_but_count_on_hand_set",
+                           scope: [i18n_scope_for_error, "count_on_hand"])
+    errors.add(:count_on_hand, error_message)
+  end
+
+  def disallow_count_on_hand_if_on_demand
+    return unless on_demand? && count_on_hand.present?
+
+    error_message = I18n.t("on_demand_but_count_on_hand_set",
+                           scope: [i18n_scope_for_error, "count_on_hand"])
+    errors.add(:count_on_hand, error_message)
+  end
+
+  def require_count_on_hand_if_limited_stock
+    return unless on_demand == false && count_on_hand.blank?
+
+    error_message = I18n.t("limited_stock_but_no_count_on_hand",
+                           scope: [i18n_scope_for_error, "count_on_hand"])
+    errors.add(:count_on_hand, error_message)
+  end
+
+  def i18n_scope_for_error
+    "activerecord.errors.models.variant_override"
+  end
 end
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 1b04166115..4962171a82 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -47,6 +47,11 @@ en:
           attributes:
             orders_close_at:
               after_orders_open_at: must be after open date
+        variant_override:
+          count_on_hand:
+            using_producer_stock_settings_but_count_on_hand_set: "must be blank because using producer stock settings"
+            on_demand_but_count_on_hand_set: "must be blank if on demand"
+            limited_stock_but_no_count_on_hand: "must be specified because forcing limited stock"
   activemodel:
     errors:
       models:
diff --git a/spec/models/variant_override_spec.rb b/spec/models/variant_override_spec.rb
index bb799f8603..258971e110 100644
--- a/spec/models/variant_override_spec.rb
+++ b/spec/models/variant_override_spec.rb
@@ -35,6 +35,81 @@ describe VariantOverride do
     end
   end
 
+  describe "validation" do
+    describe "ensuring that on_demand and count_on_hand are compatible" do
+      let(:variant_override) { build(:variant_override, hub: hub, variant: variant,
+                                     on_demand: on_demand, count_on_hand: count_on_hand) }
+
+      context "when using producer stock settings" do
+        let(:on_demand) { nil }
+
+        context "when count_on_hand is blank" do
+          let(:count_on_hand) { nil }
+
+          it "is valid" do
+            expect(variant_override.save).to be_truthy
+          end
+        end
+
+        context "when count_on_hand is set" do
+          let(:count_on_hand) { 1 }
+
+          it "is invalid" do
+            expect(variant_override.save).to be_falsey
+            error_message = I18n.t("using_producer_stock_settings_but_count_on_hand_set",
+                                   scope: [i18n_scope_for_error, "count_on_hand"])
+            expect(variant_override.errors[:count_on_hand]).to eq([error_message])
+          end
+        end
+      end
+
+      context "when on demand" do
+        let(:on_demand) { true }
+
+        context "when count_on_hand is blank" do
+          let(:count_on_hand) { nil }
+
+          it "is valid" do
+            expect(variant_override.save).to be_truthy
+          end
+        end
+
+        context "when count_on_hand is set" do
+          let(:count_on_hand) { 1 }
+
+          it "is invalid" do
+            expect(variant_override.save).to be_falsey
+            error_message = I18n.t("on_demand_but_count_on_hand_set",
+                                   scope: [i18n_scope_for_error, "count_on_hand"])
+            expect(variant_override.errors[:count_on_hand]).to eq([error_message])
+          end
+        end
+      end
+
+      context "when limited stock" do
+        let(:on_demand) { false }
+
+        context "when count_on_hand is blank" do
+          let(:count_on_hand) { nil }
+
+          it "is invalid" do
+            expect(variant_override.save).to be_falsey
+            error_message = I18n.t("limited_stock_but_no_count_on_hand",
+                                   scope: [i18n_scope_for_error, "count_on_hand"])
+            expect(variant_override.errors[:count_on_hand]).to eq([error_message])
+          end
+        end
+
+        context "when count_on_hand is set" do
+          let(:count_on_hand) { 1 }
+
+          it "is valid" do
+            expect(variant_override.save).to be_truthy
+          end
+        end
+      end
+    end
+  end
 
   describe "callbacks" do
     let!(:vo) { create(:variant_override, hub: hub, variant: variant) }
@@ -51,7 +126,6 @@ describe VariantOverride do
     end
   end
 
-
   describe "looking up prices" do
     it "returns the numeric price when present" do
       VariantOverride.create!(variant: variant, hub: hub, price: 12.34)
@@ -65,7 +139,7 @@ describe VariantOverride do
 
   describe "looking up count on hand" do
     it "returns the numeric stock level when present" do
-      VariantOverride.create!(variant: variant, hub: hub, count_on_hand: 12)
+      VariantOverride.create!(variant: variant, hub: hub, count_on_hand: 12, on_demand: false)
       VariantOverride.count_on_hand_for(hub, variant).should == 12
     end
 
@@ -76,12 +150,12 @@ describe VariantOverride do
 
   describe "checking if stock levels have been overriden" do
     it "returns true when stock level has been overridden" do
-      create(:variant_override, variant: variant, hub: hub, count_on_hand: 12)
+      create(:variant_override, variant: variant, hub: hub, on_demand: false, count_on_hand: 12)
       VariantOverride.stock_overridden?(hub, variant).should be true
     end
 
     it "returns false when the override has no stock level" do
-      create(:variant_override, variant: variant, hub: hub, count_on_hand: nil)
+      create(:variant_override, variant: variant, hub: hub, on_demand: nil, count_on_hand: nil)
       VariantOverride.stock_overridden?(hub, variant).should be false
     end
 
@@ -157,4 +231,8 @@ describe VariantOverride do
   context "extends LocalizedNumber" do
     it_behaves_like "a model using the LocalizedNumber module", [:price]
   end
+
+  def i18n_scope_for_error
+    "activerecord.errors.models.variant_override"
+  end
 end