diff --git a/app/models/budget/ballot.rb b/app/models/budget/ballot.rb
index 560075f97..550efd345 100644
--- a/app/models/budget/ballot.rb
+++ b/app/models/budget/ballot.rb
@@ -7,6 +7,10 @@ class Budget
     has_many :lines, dependent: :destroy
     has_many :investments, through: :lines
 
+    def add_investment(investment)
+      lines.create!(budget: budget, investment: investment, heading: investment.heading, group_id: investment.heading.group_id)
+    end
+
     def total_amount_spent
       investments.sum(:price).to_i
     end
@@ -18,5 +22,15 @@ class Budget
     def amount_available(heading)
       budget.heading_price(heading) - amount_spent(heading.id)
     end
+
+    def valid_heading?(heading)
+      group = heading.group
+      return false if group.budget_id != budget_id
+
+      line = lines.where(heading_id: group.heading_ids).first
+      return false if line.present? && line.heading_id != heading.id
+
+      true
+    end
   end
 end
diff --git a/app/models/budget/investment.rb b/app/models/budget/investment.rb
index 1e0d368f3..6d969f226 100644
--- a/app/models/budget/investment.rb
+++ b/app/models/budget/investment.rb
@@ -21,6 +21,7 @@ class Budget
     validates :title, presence: true
     validates :author, presence: true
     validates :description, presence: true
+    validates :heading_id, presence: true
     validates_presence_of :unfeasibility_explanation, if: :unfeasibility_explanation_required?
 
     validates :title, length: { in: 4 .. Budget::Investment.title_max_length }
@@ -152,7 +153,7 @@ class Budget
     def reason_for_not_being_ballotable_by(user, ballot)
       return permission_problem(user)    if permission_problem?(user)
       return :no_ballots_allowed         unless budget.balloting?
-      return :different_heading_assigned unless heading_id.blank? || ballot.blank? || heading_id == ballot.heading_id || ballot.heading_id.nil?
+      return :different_heading_assigned unless ballot.valid_heading?(heading)
       return :not_enough_money           if ballot.present? && !enough_money?(ballot)
     end
 
diff --git a/spec/models/budget/ballot_spec.rb b/spec/models/budget/ballot_spec.rb
index a0997a1c3..d49a3d8fb 100644
--- a/spec/models/budget/ballot_spec.rb
+++ b/spec/models/budget/ballot_spec.rb
@@ -4,32 +4,38 @@ describe Budget::Ballot do
 
   describe "#amount_spent" do
     it "returns the total amount spent in investments" do
-      inv1 = create(:budget_investment, :feasible, price: 10000)
-      inv2 = create(:budget_investment, :feasible, price: 20000)
+      budget = create(:budget)
+      group1 = create(:budget_group, budget: budget)
+      group2 = create(:budget_group, budget: budget)
+      heading1 = create(:budget_heading, group: group1, price: 100000)
+      heading2 = create(:budget_heading, group: group2, price: 200000)
+      inv1 = create(:budget_investment, :feasible, price: 10000, heading: heading1)
+      inv2 = create(:budget_investment, :feasible, price: 20000, heading: heading2)
 
-      ballot = create(:budget_ballot)
-      ballot.investments << inv1
+      ballot = create(:budget_ballot, budget: budget)
+      ballot.add_investment inv1
 
       expect(ballot.total_amount_spent).to eq 10000
 
-      ballot.investments << inv2
+      ballot.add_investment inv2
 
       expect(ballot.total_amount_spent).to eq 30000
     end
 
     it "returns the amount spent on all investments assigned to a specific heading" do
       heading = create(:budget_heading)
+      budget = heading.group.budget
       inv1 = create(:budget_investment, :feasible, price: 10000, heading: heading)
-      inv2 = create(:budget_investment, :feasible, price: 20000, heading: create(:budget_heading))
+      inv2 = create(:budget_investment, :feasible, price: 20000, heading: create(:budget_heading, group: heading.group))
       inv3 = create(:budget_investment, :feasible, price: 40000, heading: heading)
 
-      ballot = create(:budget_ballot)
-      ballot.investments << inv1
-      ballot.investments << inv2
+      ballot = create(:budget_ballot, budget: budget)
+      ballot.add_investment inv1
+      ballot.add_investment inv2
 
       expect(ballot.amount_spent(heading.id)).to eq 10000
 
-      ballot.investments << inv3
+      ballot.add_investment inv3
 
       expect(ballot.amount_spent(heading.id)).to eq 50000
     end
@@ -45,12 +51,12 @@ describe Budget::Ballot do
       inv3 = create(:budget_investment, :feasible, price: 400, heading: heading)
 
       ballot = create(:budget_ballot, budget: budget)
-      ballot.investments << inv1
-      ballot.investments << inv2
+      ballot.add_investment inv1
+      ballot.add_investment inv2
 
       expect(ballot.amount_available(heading)).to eq 900
 
-      ballot.investments << inv3
+      ballot.add_investment inv3
 
       expect(ballot.amount_available(heading)).to eq 500
     end
diff --git a/spec/models/budget/investment_spec.rb b/spec/models/budget/investment_spec.rb
index ac79fad78..d3dbf0d0b 100644
--- a/spec/models/budget/investment_spec.rb
+++ b/spec/models/budget/investment_spec.rb
@@ -66,7 +66,7 @@ describe Budget::Investment do
   end
 
   describe "by_admin" do
-    it "should return spending investments assigned to specific administrator" do
+    it "should return investments assigned to specific administrator" do
       investment1 = create(:budget_investment, administrator_id: 33)
       create(:budget_investment)
 
@@ -78,7 +78,7 @@ describe Budget::Investment do
   end
 
   describe "by_valuator" do
-    it "should return spending proposals assigned to specific valuator" do
+    it "should return investments assigned to specific valuator" do
       investment1 = create(:budget_investment)
       investment2 = create(:budget_investment)
       investment3 = create(:budget_investment)
@@ -99,7 +99,7 @@ describe Budget::Investment do
 
   describe "scopes" do
     describe "valuation_open" do
-      it "should return all spending proposals with false valuation_finished" do
+      it "should return all investments with false valuation_finished" do
         investment1 = create(:budget_investment, valuation_finished: true)
         investment2 = create(:budget_investment)
 
@@ -111,7 +111,7 @@ describe Budget::Investment do
     end
 
     describe "without_admin" do
-      it "should return all open spending proposals without assigned admin" do
+      it "should return all open investments without assigned admin" do
         investment1 = create(:budget_investment, valuation_finished: true)
         investment2 = create(:budget_investment, administrator: create(:administrator))
         investment3 = create(:budget_investment)
@@ -124,7 +124,7 @@ describe Budget::Investment do
     end
 
     describe "managed" do
-      it "should return all open spending proposals with assigned admin but without assigned valuators" do
+      it "should return all open investments with assigned admin but without assigned valuators" do
         investment1 = create(:budget_investment, administrator: create(:administrator))
         investment2 = create(:budget_investment, administrator: create(:administrator), valuation_finished: true)
         investment3 = create(:budget_investment, administrator: create(:administrator))
@@ -138,7 +138,7 @@ describe Budget::Investment do
     end
 
     describe "valuating" do
-      it "should return all spending proposals with assigned valuator but valuation not finished" do
+      it "should return all investments with assigned valuator but valuation not finished" do
         investment1 = create(:budget_investment)
         investment2 = create(:budget_investment)
         investment3 = create(:budget_investment, valuation_finished: true)
@@ -154,7 +154,7 @@ describe Budget::Investment do
     end
 
     describe "valuation_finished" do
-      it "should return all spending proposals with valuation finished" do
+      it "should return all investments with valuation finished" do
         investment1 = create(:budget_investment)
         investment2 = create(:budget_investment)
         investment3 = create(:budget_investment, valuation_finished: true)
@@ -170,7 +170,7 @@ describe Budget::Investment do
     end
 
     describe "feasible" do
-      it "should return all feasible spending proposals" do
+      it "should return all feasible investments" do
         feasible_investment = create(:budget_investment, :feasible)
         create(:budget_investment)
 
@@ -179,7 +179,7 @@ describe Budget::Investment do
     end
 
     describe "unfeasible" do
-      it "should return all unfeasible spending proposals" do
+      it "should return all unfeasible investments" do
         unfeasible_investment = create(:budget_investment, :unfeasible)
         create(:budget_investment, :feasible)
 
@@ -283,12 +283,12 @@ describe Budget::Investment do
 
   describe "#with_supports" do
     it "should return proposals with supports" do
-      sp1 = create(:budget_investment)
-      sp2 = create(:budget_investment)
-      create(:vote, votable: sp1)
+      inv1 = create(:budget_investment)
+      inv2 = create(:budget_investment)
+      create(:vote, votable: inv1)
 
-      expect(Budget::Investment.with_supports).to include(sp1)
-      expect(Budget::Investment.with_supports).to_not include(sp2)
+      expect(Budget::Investment.with_supports).to include(inv1)
+      expect(Budget::Investment.with_supports).to_not include(inv2)
     end
   end
 
@@ -327,11 +327,9 @@ describe Budget::Investment do
           expect(investment.reason_for_not_being_ballotable_by(user, ballot)).to be_nil
         end
 
-        it "accepts valid district selections" do
+        it "accepts valid selections" do
           budget.phase = "selecting"
           expect(investment.reason_for_not_being_selectable_by(user)).to be_nil
-          ballot.heading_id = heading.id
-          expect(investment.reason_for_not_being_selectable_by(user)).to be_nil
         end
 
         it "rejects users with different headings" do
@@ -340,22 +338,25 @@ describe Budget::Investment do
           california = create(:budget_heading, group: group)
           new_york = create(:budget_heading, group: group)
 
-          sp1 = create(:budget_investment, :feasible, heading: california)
-          sp2 = create(:budget_investment, :feasible, heading: new_york)
-          b = create(:budget_ballot, user: user, heading: california, investments: [sp1])
+          inv1 = create(:budget_investment, :feasible, heading: california)
+          inv2 = create(:budget_investment, :feasible, heading: new_york)
+          b = create(:budget_ballot, user: user, budget: budget)
+          b.add_investment inv1
 
-          expect(sp2.reason_for_not_being_ballotable_by(user, b)).to eq(:different_heading_assigned)
+          expect(inv2.reason_for_not_being_ballotable_by(user, b)).to eq(:different_heading_assigned)
         end
 
         it "rejects proposals with price higher than current available money" do
           budget.phase = "balloting"
           distritos = create(:budget_group, budget: budget)
           carabanchel = create(:budget_heading, group: distritos, price: 35)
-          sp1 = create(:budget_investment, :feasible, heading: carabanchel, price: 30)
-          sp2 = create(:budget_investment, :feasible, heading: carabanchel, price: 10)
-          ballot = create(:budget_ballot, user: user, heading: carabanchel, investments: [sp1])
+          inv1 = create(:budget_investment, :feasible, heading: carabanchel, price: 30)
+          inv2 = create(:budget_investment, :feasible, heading: carabanchel, price: 10)
 
-          expect(sp2.reason_for_not_being_ballotable_by(user, ballot)).to eq(:not_enough_money)
+          ballot = create(:budget_ballot, user: user, budget: budget)
+          ballot.add_investment inv1
+
+          expect(inv2.reason_for_not_being_ballotable_by(user, ballot)).to eq(:not_enough_money)
         end
 
       end