diff --git a/app/Helpers/Invoice/ProRata.php b/app/Helpers/Invoice/ProRata.php
index c27394662c2c..e3291b25c218 100644
--- a/app/Helpers/Invoice/ProRata.php
+++ b/app/Helpers/Invoice/ProRata.php
@@ -34,7 +34,7 @@ class ProRata
      */
     public function refund(float $amount, Carbon $from_date, Carbon $to_date, int $frequency) :float
     {
-        $days = $from_date->diffInDays($to_date);
+        $days = $from_date->copy()->diffInDays($to_date);
         $days_in_frequency = $this->getDaysInFrequency($frequency);
 
         return round( (($days/$days_in_frequency) * $amount),2);
@@ -52,9 +52,12 @@ class ProRata
      */
     public function charge(float $amount, Carbon $from_date, Carbon $to_date, int $frequency) :float
     {
-        $days = $from_date->diffInDays($to_date);
+        $days = $from_date->copy()->diffInDays($to_date);
         $days_in_frequency = $this->getDaysInFrequency($frequency);
-
+nlog($from_date->format('Y-m-d'));
+nlog($days);
+nlog($days_in_frequency);
+nlog($amount);
         return round( (($days/$days_in_frequency) * $amount),2);
     }
 
diff --git a/app/Helpers/Subscription/SubscriptionCalculator.php b/app/Helpers/Subscription/SubscriptionCalculator.php
index 3956ef4617ff..18dc20cd2d01 100644
--- a/app/Helpers/Subscription/SubscriptionCalculator.php
+++ b/app/Helpers/Subscription/SubscriptionCalculator.php
@@ -15,6 +15,7 @@ use App\Helpers\Invoice\ProRata;
 use App\Models\Invoice;
 use App\Models\RecurringInvoice;
 use App\Models\Subscription;
+use Illuminate\Support\Carbon;
 
 /**
  * SubscriptionCalculator.
@@ -24,7 +25,7 @@ class SubscriptionCalculator
 
     public Subscription $target_subscription;
 
-    public Invoice $invoice
+    public Invoice $invoice;
 
     public function __construct(Subscription $target_subscription, Invoice $invoice)
     {
@@ -57,6 +58,8 @@ class SubscriptionCalculator
         //set the starting refund amount
         $refund_amount = 0;
 
+        $refund_invoice = false;
+
         //are they paid up to date.
 
         //yes - calculate refund
@@ -68,7 +71,7 @@ class SubscriptionCalculator
             $subscription = Subscription::find($this->invoice->subscription_id);
             $pro_rata = new ProRata();
 
-            $to_date = $subscription->getNextDateForFrequency(Carbon::parse($refund_invoice->date), $subscription->frequency_id); 
+            $to_date = $subscription->service()->getNextDateForFrequency(Carbon::parse($refund_invoice->date), $subscription->frequency_id); 
 
             $refund_amount = $pro_rata->refund($refund_invoice->amount, now(), $to_date, $subscription->frequency_id);
 
@@ -88,11 +91,9 @@ class SubscriptionCalculator
 
     private function getRefundInvoice()
     {
-
         return Invoice::where('subscription_id', $this->invoice->subscription_id)
                       ->where('client_id', $this->invoice->client_id)
                       ->where('is_deleted', 0)
-                      ->where('balance', '>', 0)
                       ->orderBy('id', 'desc')
                       ->first();
 
diff --git a/database/factories/SubscriptionFactory.php b/database/factories/SubscriptionFactory.php
index 63bff1c98914..db73008bb34a 100644
--- a/database/factories/SubscriptionFactory.php
+++ b/database/factories/SubscriptionFactory.php
@@ -33,7 +33,8 @@ class SubscriptionFactory extends Factory
     public function definition()
     {
         return [
-            'frequency_id' => RecurringInvoice::FREQUENCY_MONTHLY
+            'frequency_id' => RecurringInvoice::FREQUENCY_MONTHLY,
+            'name' => $this->faker->company(),
         ];
     }
 }
diff --git a/tests/Unit/SubscriptionsCalcTest.php b/tests/Unit/SubscriptionsCalcTest.php
index 7100f25b8533..61a0adad81bd 100644
--- a/tests/Unit/SubscriptionsCalcTest.php
+++ b/tests/Unit/SubscriptionsCalcTest.php
@@ -10,8 +10,11 @@
  */
 namespace Tests\Unit;
 
+use App\Helpers\Invoice\ProRata;
+use App\Helpers\Subscription\SubscriptionCalculator;
 use App\Models\Invoice;
 use App\Models\Subscription;
+use Illuminate\Support\Carbon;
 use Tests\MockUnitData;
 use Tests\TestCase;
 
@@ -41,7 +44,13 @@ class SubscriptionsCalcTest extends TestCase
             'company_id' => $this->company->id,
             'user_id' => $this->user->id,
             'price' => 10,
+        ]);
 
+
+        $target = Subscription::factory()->create([
+            'company_id' => $this->company->id,
+            'user_id' => $this->user->id,
+            'price' => 20,
         ]);
 
         $invoice = Invoice::factory()->create([
@@ -57,7 +66,7 @@ class SubscriptionsCalcTest extends TestCase
             'tax_name3' => '',
             'discount' => 0,
             'subscription_id' => $subscription->id,
-            'date' => now()
+            'date' => '2021-01-01',
         ]); 
 
         $invoice = $invoice->calc()->getInvoice();
@@ -69,6 +78,33 @@ class SubscriptionsCalcTest extends TestCase
         $this->assertEquals(10, $invoice->amount);
         $this->assertEquals(10, $invoice->balance);
 
+        $sub_calculator = new SubscriptionCalculator($target->fresh(), $invoice->fresh());
+
+        $this->assertFalse($sub_calculator->isPaidUp());
+
+        $invoice->service()->markPaid()->save();
+
+        $this->assertTrue($sub_calculator->isPaidUp());
+
+        $this->assertEquals(10, $invoice->amount);
+        $this->assertEquals(0, $invoice->balance);
+
+        $pro_rata = new ProRata();
+
+        $refund = $pro_rata->refund($invoice->amount, Carbon::parse('2021-01-01'), Carbon::parse('2021-01-06'), $subscription->frequency_id);
+
+        $this->assertEquals(1.61, $refund);
+
+        $pro_rata = new ProRata();
+
+        $upgrade = $pro_rata->charge($target->price, Carbon::parse('2021-01-01'), Carbon::parse('2021-01-06'), $subscription->frequency_id);
+
+        $this->assertEquals(3.23, $upgrade);
+
+        // $net_upgrade_price = $sub_calculator->calcUpgradePlan();
+
+        // $this->assertEquals(1.62, $net_upgrade_price);
+
     }