diff --git a/app/models/invoice.rb b/app/models/invoice.rb
index 87f27af36..adaad87d6 100644
--- a/app/models/invoice.rb
+++ b/app/models/invoice.rb
@@ -117,10 +117,10 @@ class Invoice < ApplicationRecord
     return unless registrar_user
 
     vat = VatRateCalculator.new(registrar: registrar_user).calculate
-    wo_vat = transaction.sum / (1 + (vat / 100))
-    registrar_user.issue_prepayment_invoice(amount: wo_vat,
-                                            description: 'Direct top-up via bank transfer',
-                                            payable: false)
+    wo_vat = (transaction.sum / (1 + (vat / 100)))
+
+    registrar_user.issue_prepayment_invoice(wo_vat, 'Direct top-up via bank transfer',
+                                            payable: false, total: transaction.sum)
   end
 
   private
diff --git a/app/models/registrar.rb b/app/models/registrar.rb
index 86ff5ef4d..42fbc2b78 100644
--- a/app/models/registrar.rb
+++ b/app/models/registrar.rb
@@ -54,7 +54,7 @@ class Registrar < ApplicationRecord
     end
   end
 
-  def issue_prepayment_invoice(amount, description = nil, payable: true)
+  def issue_prepayment_invoice(amount, description = nil, payable: true, total: nil)
     vat_rate = ::Invoice::VatRateCalculator.new(registrar: self).calculate
 
     invoice = invoices.create!(
@@ -90,6 +90,7 @@ class Registrar < ApplicationRecord
       buyer_email: email,
       reference_no: reference_no,
       vat_rate: vat_rate,
+      total: total,
       items_attributes: [
         {
           description: 'prepayment',
diff --git a/test/models/invoice_test.rb b/test/models/invoice_test.rb
index 9c1c45610..6ee2dc85c 100644
--- a/test/models/invoice_test.rb
+++ b/test/models/invoice_test.rb
@@ -109,4 +109,16 @@ class InvoiceTest < ActiveSupport::TestCase
                           seller_zip: nil)
     assert_equal 'street, city, state', invoice.seller_address
   end
+
+  def test_assumes_correct_sum_amount_when_created_by_transaction
+    registrar = registrars(:bestnames)
+
+    bank_transaction = bank_transactions(:one).dup
+    bank_transaction.reference_no = registrar.reference_no
+    bank_transaction.sum = 5
+    bank_transaction.save
+
+    invoice = Invoice.create_from_transaction!(bank_transaction)
+    assert_equal 5, invoice.total
+  end
 end
diff --git a/test/tasks/invoices/process_payments_test.rb b/test/tasks/invoices/process_payments_test.rb
index 38c2e8fdc..eeaf411cc 100644
--- a/test/tasks/invoices/process_payments_test.rb
+++ b/test/tasks/invoices/process_payments_test.rb
@@ -94,6 +94,13 @@ class ProcessPaymentsTaskTest < ActiveSupport::TestCase
     end
   end
 
+  def test_topup_creates_invoice_with_total_of_transactioned_amount
+    registrar = registrars(:bestnames)
+    run_task
+
+    assert_equal 0.1, registrar.invoices.last.total
+  end
+
   def test_output
     assert_output "Transactions processed: 1\n" do
       run_task