diff --git a/db/migrate/20191024153351_add_invoice_items_quantity_constraint.rb b/db/migrate/20191024153351_add_invoice_items_quantity_constraint.rb
new file mode 100644
index 000000000..9f99fa607
--- /dev/null
+++ b/db/migrate/20191024153351_add_invoice_items_quantity_constraint.rb
@@ -0,0 +1,14 @@
+class AddInvoiceItemsQuantityConstraint < ActiveRecord::Migration
+  def up
+    execute <<~SQL
+      ALTER TABLE invoice_items ADD CONSTRAINT invoice_items_quantity_is_positive
+      CHECK (quantity > 0);
+    SQL
+  end
+
+  def down
+    execute <<~SQL
+      ALTER TABLE invoice_items DROP CONSTRAINT invoice_items_quantity_is_positive;
+    SQL
+  end
+end
diff --git a/db/migrate/20191024160038_add_invoices_due_date_constraint.rb b/db/migrate/20191024160038_add_invoices_due_date_constraint.rb
new file mode 100644
index 000000000..313f5d276
--- /dev/null
+++ b/db/migrate/20191024160038_add_invoices_due_date_constraint.rb
@@ -0,0 +1,14 @@
+class AddInvoicesDueDateConstraint < ActiveRecord::Migration
+  def up
+    execute <<~SQL
+      ALTER TABLE invoices ADD CONSTRAINT invoices_due_date_is_not_before_issue_date
+      CHECK (due_date >= issue_date);
+    SQL
+  end
+
+  def down
+    execute <<~SQL
+      ALTER TABLE invoices DROP CONSTRAINT invoices_due_date_is_not_before_issue_date;
+    SQL
+  end
+end
diff --git a/db/structure.sql b/db/structure.sql
index 3382e9984..c487fbf87 100644
--- a/db/structure.sql
+++ b/db/structure.sql
@@ -899,7 +899,8 @@ CREATE TABLE public.invoice_items (
     created_at timestamp without time zone,
     updated_at timestamp without time zone,
     creator_str character varying,
-    updator_str character varying
+    updator_str character varying,
+    CONSTRAINT invoice_items_quantity_is_positive CHECK ((quantity > 0))
 );
 
 
@@ -968,7 +969,8 @@ CREATE TABLE public.invoices (
     total numeric(10,2) NOT NULL,
     in_directo boolean DEFAULT false,
     buyer_vat_no character varying,
-    issue_date date NOT NULL
+    issue_date date NOT NULL,
+    CONSTRAINT invoices_due_date_is_not_before_issue_date CHECK ((due_date >= issue_date))
 );
 
 
@@ -4878,3 +4880,7 @@ INSERT INTO schema_migrations (version) VALUES ('20191007123000');
 
 INSERT INTO schema_migrations (version) VALUES ('20191008024334');
 
+INSERT INTO schema_migrations (version) VALUES ('20191024153351');
+
+INSERT INTO schema_migrations (version) VALUES ('20191024160038');
+
diff --git a/test/models/invoice_test.rb b/test/models/invoice_test.rb
index 6e6971139..9c1c45610 100644
--- a/test/models/invoice_test.rb
+++ b/test/models/invoice_test.rb
@@ -11,7 +11,8 @@ class InvoiceTest < ActiveSupport::TestCase
 
   def test_overdue_scope_returns_unpaid_uncancelled_invoices_with_past_due_date
     travel_to Time.zone.parse('2010-07-05')
-    @invoice.update!(account_activity: nil, cancelled_at: nil, due_date: '2010-07-04')
+    @invoice.update!(account_activity: nil, cancelled_at: nil, issue_date: '2010-07-04',
+                     due_date: '2010-07-04')
 
     assert Invoice.overdue.include?(@invoice), 'Should return overdue invoice'
   end
@@ -108,4 +109,4 @@ class InvoiceTest < ActiveSupport::TestCase
                           seller_zip: nil)
     assert_equal 'street, city, state', invoice.seller_address
   end
-end
\ No newline at end of file
+end
diff --git a/test/services/overdue_invoice_canceller_test.rb b/test/services/overdue_invoice_canceller_test.rb
index debade3a9..bc3447484 100644
--- a/test/services/overdue_invoice_canceller_test.rb
+++ b/test/services/overdue_invoice_canceller_test.rb
@@ -2,7 +2,6 @@ require 'test_helper'
 
 class OverdueInvoiceCancellerTest < ActiveSupport::TestCase
   setup do
-    @invoice = invoices(:one)
     @original_days_to_keep_overdue_invoices_active = Setting.days_to_keep_overdue_invoices_active
   end
 
@@ -28,26 +27,24 @@ class OverdueInvoiceCancellerTest < ActiveSupport::TestCase
 
   def test_cancels_overdue_invoices
     travel_to Time.zone.parse('2010-07-05')
-    @invoice.update!(account_activity: nil, cancelled_at: nil, due_date: '2010-07-03')
-    assert @invoice.cancellable?
+    invoice = cancellable_invoice(due_date: '2010-07-03')
 
     canceller = OverdueInvoiceCanceller.new(delay: 1.day)
     canceller.cancel
-    @invoice.reload
+    invoice.reload
 
-    assert @invoice.cancelled?
+    assert invoice.cancelled?
   end
 
   def test_yields_cancelled_invoices
     travel_to Time.zone.parse('2010-07-05')
-    @invoice.update!(account_activity: nil, cancelled_at: nil, due_date: '2010-07-03')
-    assert @invoice.cancellable?
+    invoice = cancellable_invoice(due_date: '2010-07-03')
 
     canceller = OverdueInvoiceCanceller.new(delay: 1.day)
 
     iteration_count = 0
-    canceller.cancel do |invoice|
-      assert_equal @invoice, invoice
+    canceller.cancel do |cancelled_invoice|
+      assert_equal invoice, cancelled_invoice
       iteration_count += 1
     end
     assert_equal 1, iteration_count
@@ -55,13 +52,21 @@ class OverdueInvoiceCancellerTest < ActiveSupport::TestCase
 
   def test_keeps_not_overdue_invoices_intact
     travel_to Time.zone.parse('2010-07-05')
-    @invoice.update!(account_activity: nil, cancelled_at: nil, due_date: '2010-07-04')
-    assert @invoice.cancellable?
+    invoice = cancellable_invoice(due_date: '2010-07-04')
 
     canceller = OverdueInvoiceCanceller.new(delay: 1.day)
     canceller.cancel
-    @invoice.reload
+    invoice.reload
 
-    assert @invoice.not_cancelled?
+    assert invoice.not_cancelled?
   end
-end
\ No newline at end of file
+
+  private
+
+  def cancellable_invoice(due_date:)
+    invoice = invoices(:one)
+    invoice.update!(account_activity: nil, cancelled_at: nil, issue_date: due_date,
+                    due_date: due_date)
+    invoice
+  end
+end