diff --git a/app/Helpers/Invoice/InvoiceSum.php b/app/Helpers/Invoice/InvoiceSum.php
index 349d0271c36c..2aeb3e962194 100644
--- a/app/Helpers/Invoice/InvoiceSum.php
+++ b/app/Helpers/Invoice/InvoiceSum.php
@@ -242,9 +242,9 @@ class InvoiceSum
 
         if ($this->invoice->status_id != Invoice::STATUS_DRAFT) {
             if ($this->invoice->amount != $this->invoice->balance) {
-                $paid_to_date = $this->invoice->amount - $this->invoice->balance;
+                // $paid_to_date = $this->invoice->amount - $this->invoice->balance;
 
-                $this->invoice->balance = Number::roundValue($this->getTotal(), $this->precision) - $paid_to_date;
+                $this->invoice->balance = Number::roundValue($this->getTotal(), $this->precision) - $this->invoice->paid_to_date;
             } else {
                 $this->invoice->balance = Number::roundValue($this->getTotal(), $this->precision);
             }
diff --git a/app/Helpers/Invoice/InvoiceSumInclusive.php b/app/Helpers/Invoice/InvoiceSumInclusive.php
index 9afbe1c76db7..8a7df5e68def 100644
--- a/app/Helpers/Invoice/InvoiceSumInclusive.php
+++ b/app/Helpers/Invoice/InvoiceSumInclusive.php
@@ -259,9 +259,9 @@ class InvoiceSumInclusive
         /* If amount != balance then some money has been paid on the invoice, need to subtract this difference from the total to set the new balance */
         if ($this->invoice->status_id != Invoice::STATUS_DRAFT) {
             if ($this->invoice->amount != $this->invoice->balance) {
-                $paid_to_date = $this->invoice->amount - $this->invoice->balance;
+                // $paid_to_date = $this->invoice->amount - $this->invoice->balance;
 
-                $this->invoice->balance = $this->formatValue($this->getTotal(), $this->precision) - $paid_to_date;
+                $this->invoice->balance = $this->formatValue($this->getTotal(), $this->precision) - $this->invoice->paid_to_date;
             } else {
                 $this->invoice->balance = $this->formatValue($this->getTotal(), $this->precision);
             }
diff --git a/tests/Unit/InvoiceBalanceTest.php b/tests/Unit/InvoiceBalanceTest.php
new file mode 100644
index 000000000000..d3e31b6479ad
--- /dev/null
+++ b/tests/Unit/InvoiceBalanceTest.php
@@ -0,0 +1,241 @@
+<?php
+/**
+ * Invoice Ninja (https://invoiceninja.com).
+ *
+ * @link https://github.com/invoiceninja/invoiceninja source repository
+ *
+ * @copyright Copyright (c) 2021. Invoice Ninja LLC (https://invoiceninja.com)
+ *
+ * @license https://www.elastic.co/licensing/elastic-license
+ */
+
+namespace Tests\Unit;
+
+use App\DataMapper\InvoiceItem;
+use App\Models\Invoice;
+use App\Models\PurchaseOrder;
+use Illuminate\Foundation\Testing\DatabaseTransactions;
+use Tests\MockAccountData;
+use Tests\TestCase;
+
+/**
+ * @test
+ * @covers  App\Helpers\Invoice\InvoiceSum
+ */
+class InvoiceBalanceTest extends TestCase
+{
+    use MockAccountData;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $this->makeTestData();
+    }
+
+    public function testInvoiceBalances()
+    {
+        
+        $item = new InvoiceItem();
+        $item->quantity = 1;
+        $item->cost = 100;
+        $item->type_id = '1';
+        
+        $i = Invoice::factory()->create([
+            'company_id' => $this->company->id,
+            'user_id' => $this->user->id,
+            'client_id' => $this->client->id,
+            'line_items' => [$item],
+            'status_id' => 1,
+            'tax_rate1' => 0,
+            'tax_rate2' => 0,
+            'tax_rate3' => 0,
+            'tax_name1' => '',
+            'tax_name2' => '',
+            'tax_name3' => '',
+            'discount' => 0,
+            'paid_to_date' => 0,
+        ]);
+
+
+        $this->assertEquals(1, $i->status_id);
+
+        $i = $i->calc()->getInvoice()->service()->markSent()->save();
+
+        $this->assertEquals(100, $i->amount);
+        $this->assertEquals(100, $i->balance);
+        $this->assertEquals(2, $i->status_id);
+        $this->assertEquals(0, $i->paid_to_date);
+
+        
+        $item = new InvoiceItem();
+        $item->quantity = 1;
+        $item->cost = 30.37;
+        $item->type_id = '1';
+
+        $i->line_items = [$item];
+
+        $i = $i->calc()->getInvoice();
+
+        // nlog($i->withoutRelations()->toArray());
+
+        $this->assertEquals(30.37, $i->amount);
+        $this->assertEquals(30.37, $i->balance);
+        $this->assertEquals(2, $i->status_id);
+        $this->assertEquals(0, $i->paid_to_date);
+
+        $i = $i->service()->applyPaymentAmount(10.37, 'paid')->save();
+        
+        // nlog($i->withoutRelations()->toArray());
+
+        $this->assertEquals(30.37, $i->amount);
+        $this->assertEquals(20.00, $i->balance);
+        $this->assertEquals(3, $i->status_id);
+        $this->assertEquals(10.37, $i->paid_to_date);
+
+        $item = new InvoiceItem();
+        $item->quantity = 1;
+        $item->cost = 15;
+        $item->type_id = '1';
+
+        $i->line_items = [$item];
+
+        $i = $i->calc()->getInvoice();
+
+        $this->assertEquals(15, $i->amount);
+        $this->assertEquals(15-10.37, $i->balance);
+        $this->assertEquals(3, $i->status_id);
+        $this->assertEquals(10.37, $i->paid_to_date);
+
+
+    }
+
+
+    public function testInvoiceBalancesWithNegatives()
+    {
+        
+        $item = new InvoiceItem();
+        $item->quantity = 1;
+        $item->cost = -100;
+        $item->type_id = '1';
+        
+        $i = Invoice::factory()->create([
+            'company_id' => $this->company->id,
+            'user_id' => $this->user->id,
+            'client_id' => $this->client->id,
+            'line_items' => [$item],
+            'status_id' => 1,
+            'tax_rate1' => 0,
+            'tax_rate2' => 0,
+            'tax_rate3' => 0,
+            'tax_name1' => '',
+            'tax_name2' => '',
+            'tax_name3' => '',
+            'discount' => 0,
+            'paid_to_date' => 0,
+        ]);
+
+
+        $this->assertEquals(1, $i->status_id);
+
+        $i = $i->calc()->getInvoice()->service()->markSent()->save();
+
+        $this->assertEquals(-100, $i->amount);
+        $this->assertEquals(-100, $i->balance);
+        $this->assertEquals(2, $i->status_id);
+        $this->assertEquals(0, $i->paid_to_date);
+
+        
+        $item = new InvoiceItem();
+        $item->quantity = 1;
+        $item->cost = -30.37;
+        $item->type_id = '1';
+
+        $i->line_items = [$item];
+
+        $i = $i->calc()->getInvoice();
+
+        $this->assertEquals(-30.37, $i->amount);
+        $this->assertEquals(-30.37, $i->balance);
+        $this->assertEquals(2, $i->status_id);
+        $this->assertEquals(0, $i->paid_to_date);
+
+        $i = $i->service()->markPaid()->save();
+
+        $this->assertEquals(0, $i->balance);
+        $this->assertEquals(-30.37, $i->paid_to_date);
+    }
+
+
+
+
+    public function testPurchaseOrderBalances()
+    {
+        
+        $item = new InvoiceItem();
+        $item->quantity = 1;
+        $item->cost = 100;
+        $item->type_id = '1';
+        
+        $i = PurchaseOrder::factory()->create([
+            'company_id' => $this->company->id,
+            'user_id' => $this->user->id,
+            'vendor_id' => $this->vendor->id,
+            'line_items' => [$item],
+            'status_id' => 1,
+            'tax_rate1' => 0,
+            'tax_rate2' => 0,
+            'tax_rate3' => 0,
+            'tax_name1' => '',
+            'tax_name2' => '',
+            'tax_name3' => '',
+            'discount' => 0,
+            'paid_to_date' => 0,
+        ]);
+
+        $this->assertEquals(1, $i->status_id);
+
+        $i = $i->calc()->getPurchaseOrder();
+        $i = $i->service()->markSent()->save();
+
+        $this->assertEquals(100, $i->amount);
+        $this->assertEquals(100, $i->balance);
+        $this->assertEquals(2, $i->status_id);
+        $this->assertEquals(0, $i->paid_to_date);
+
+        
+        $item = new InvoiceItem();
+        $item->quantity = 1;
+        $item->cost = 30.37;
+        $item->type_id = '1';
+
+        $i->line_items = [$item];
+
+        $i = $i->calc()->getPurchaseOrder();
+        $i = $i->service()->markSent()->save();
+
+        $this->assertEquals(30.37, $i->amount);
+        $this->assertEquals(30.37, $i->balance);
+        $this->assertEquals(2, $i->status_id);
+        $this->assertEquals(0, $i->paid_to_date);
+
+        $item = new InvoiceItem();
+        $item->quantity = 1;
+        $item->cost =10.37;
+        $item->type_id = '1';
+
+        $i->line_items = [$item];
+
+        $i = $i->calc()->getPurchaseOrder();
+        $i = $i->service()->markSent()->save();
+
+        $this->assertEquals(10.37, $i->amount);
+        $this->assertEquals(10.37, $i->balance);
+        $this->assertEquals(2, $i->status_id);
+        $this->assertEquals(0, $i->paid_to_date);
+
+
+
+    }
+
+}