diff --git a/app/Http/Requests/Login/LoginRequest.php b/app/Http/Requests/Login/LoginRequest.php
index 7d0ab21d8cb0..42aed76b9374 100644
--- a/app/Http/Requests/Login/LoginRequest.php
+++ b/app/Http/Requests/Login/LoginRequest.php
@@ -36,7 +36,7 @@ class LoginRequest extends Request
     public function rules()
     {
         if (Ninja::isHosted()) {
-            $email_rules = ['required', new BlackListRule, new EmailBlackListRule];
+            $email_rules = ['required', new EmailBlackListRule];
         } else {
             $email_rules = 'required';
         }
diff --git a/app/Models/Client.php b/app/Models/Client.php
index a72dd3344c29..8272e2fc10a5 100644
--- a/app/Models/Client.php
+++ b/app/Models/Client.php
@@ -812,6 +812,15 @@ class Client extends BaseModel implements HasLocalePreference
         return $defaults;
     }
 
+    public function setExchangeRate()
+    {
+        
+        $converter = new CurrencyApi();
+
+        return 1/$converter->convert(1, $this->currency()->id, $this->company->settings->currency_id);
+
+    }
+
     public function timezone_offset() :int
     {
         $offset = 0;
diff --git a/app/Services/Invoice/InvoiceService.php b/app/Services/Invoice/InvoiceService.php
index e435263879b1..045282f41aaf 100644
--- a/app/Services/Invoice/InvoiceService.php
+++ b/app/Services/Invoice/InvoiceService.php
@@ -567,7 +567,7 @@ class InvoiceService
 
         /* If client currency differs from the company default currency, then insert the client exchange rate on the model.*/
         if (! isset($this->invoice->exchange_rate) && $this->invoice->client->currency()->id != (int) $this->invoice->company->settings->currency_id) {
-            $this->invoice->exchange_rate = $this->invoice->client->currency()->exchange_rate;
+            $this->invoice->exchange_rate = $this->invoice->client->setExchangeRate();
         }
 
         if ($this->invoice->client->getSetting('auto_bill_standard_invoices')) {
diff --git a/database/migrations/2024_01_09_084515_product_cost_field_population.php b/database/migrations/2024_01_09_084515_product_cost_field_population.php
new file mode 100644
index 000000000000..830470d94ca9
--- /dev/null
+++ b/database/migrations/2024_01_09_084515_product_cost_field_population.php
@@ -0,0 +1,52 @@
+<?php
+
+use App\Utils\Ninja;
+use App\Models\Invoice;
+use Illuminate\Support\Facades\Schema;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Migrations\Migration;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        if(Ninja::isHosted()) {
+            return;
+        }
+        
+        set_time_limit(0);
+        
+        Invoice::withTrashed()
+            ->where('is_deleted', false)
+            ->cursor()
+            ->each(function (Invoice $invoice) {
+                
+                
+                $line_items = $invoice->line_items;
+
+                foreach ($line_items as $key => $item)
+                {
+
+                    if($item?->product_cost == 0 && $product = Product::where('company_id', $invoice->company_id)->where('product_key', $item->product_key)->where('cost', '>', 0)->first())
+                    {
+                        $line_items[$key]->product_cost = $product->cost;
+                    }
+                }
+
+                $invoice->line_items = $line_items;
+                $invoice->saveQuietly();
+
+            });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        //
+    }
+};
diff --git a/tests/Feature/ClientTest.php b/tests/Feature/ClientTest.php
index b09978d6af67..92632dad2380 100644
--- a/tests/Feature/ClientTest.php
+++ b/tests/Feature/ClientTest.php
@@ -11,25 +11,27 @@
 
 namespace Tests\Feature;
 
+use Tests\TestCase;
+use App\Models\User;
+use App\Models\Client;
+use App\Models\Credit;
+use App\Models\Account;
+use App\Models\Company;
+use App\Models\Currency;
+use Tests\MockAccountData;
+use Illuminate\Support\Str;
+use App\Models\CompanyToken;
+use App\Models\ClientContact;
+use App\Utils\Traits\MakesHash;
+use App\DataMapper\ClientSettings;
 use App\DataMapper\CompanySettings;
 use App\DataMapper\DefaultSettings;
 use App\Factory\InvoiceItemFactory;
-use App\Models\Account;
-use App\Models\Client;
-use App\Models\ClientContact;
-use App\Models\Company;
-use App\Models\CompanyToken;
-use App\Models\Credit;
-use App\Models\User;
-use App\Utils\Traits\MakesHash;
 use Illuminate\Database\Eloquent\Model;
-use Illuminate\Foundation\Testing\DatabaseTransactions;
-use Illuminate\Routing\Middleware\ThrottleRequests;
 use Illuminate\Support\Facades\Session;
-use Illuminate\Support\Str;
 use Illuminate\Validation\ValidationException;
-use Tests\MockAccountData;
-use Tests\TestCase;
+use Illuminate\Routing\Middleware\ThrottleRequests;
+use Illuminate\Foundation\Testing\DatabaseTransactions;
 
 /**
  * @test
@@ -65,6 +67,34 @@ class ClientTest extends TestCase
         $this->makeTestData();
     }
 
+    public function testClientExchangeRateCalculation()
+    {
+        $settings = ClientSettings::defaults();
+        $settings->currency_id = 12;
+
+        $c = Client::factory()
+                ->create([
+                    'company_id' => $this->company->id,
+                    'user_id' => $this->user->id,
+                    'settings' => $settings
+                ]);
+
+        $settings = $this->company->settings;
+        $settings->currency_id = '3';
+
+        $this->company->saveSettings($settings, $this->company);
+
+        $client_exchange_rate = round($c->setExchangeRate(),2);
+
+        $aud_currency = Currency::find(12);
+        $eur_currency = Currency::find(3);
+
+        $synthetic_exchange = $aud_currency->exchange_rate / $eur_currency->exchange_rate;
+
+        $this->assertEquals($client_exchange_rate, round($synthetic_exchange,2));
+
+    }
+
     public function testStoreClientFixes2()
     {
         $data = [
diff --git a/tests/Feature/ProductTest.php b/tests/Feature/ProductTest.php
index 7a709e398d33..40af31f9a9cc 100644
--- a/tests/Feature/ProductTest.php
+++ b/tests/Feature/ProductTest.php
@@ -11,14 +11,16 @@
 
 namespace Tests\Feature;
 
+use App\DataMapper\InvoiceItem;
+use Tests\TestCase;
+use App\Models\Invoice;
 use App\Models\Product;
+use Tests\MockAccountData;
 use App\Utils\Traits\MakesHash;
 use Illuminate\Database\Eloquent\Model;
-use Illuminate\Foundation\Testing\DatabaseTransactions;
-use Illuminate\Routing\Middleware\ThrottleRequests;
 use Illuminate\Support\Facades\Session;
-use Tests\MockAccountData;
-use Tests\TestCase;
+use Illuminate\Routing\Middleware\ThrottleRequests;
+use Illuminate\Foundation\Testing\DatabaseTransactions;
 
 /**
  * @test
@@ -30,6 +32,8 @@ class ProductTest extends TestCase
     use DatabaseTransactions;
     use MockAccountData;
 
+    protected $faker;
+    
     protected function setUp() :void
     {
         parent::setUp();
@@ -49,6 +53,72 @@ class ProductTest extends TestCase
 
     }
 
+    public function testProductCostMigration()
+    {
+        $items = [];
+
+        $item = new InvoiceItem();
+        $item->product_cost = 0;
+        $item->product_key = 'test';
+        $item->quantity = 1;
+        $item->cost = 10;
+        $item->notes = 'product';
+
+        $items[] = $item;
+
+        $p = Product::factory()
+            ->create([
+                'user_id' => $this->user->id,
+                'company_id' => $this->company->id,
+                'product_key' => 'test',
+                'cost' => 10,
+                'price' => 20,
+                'quantity' => 1,
+                'notes' => 'product',
+            ]);
+
+        $i = Invoice::factory()
+                ->create([
+                    'client_id' => $this->client->id,
+                    'company_id' => $this->company->id,
+                    'user_id' => $this->user->id,
+                    'line_items' => $items,
+                ]);
+
+
+        $line_items = $i->line_items;
+
+        $this->assertEquals(0, $line_items[0]->product_cost);
+
+        Invoice::withTrashed()
+            ->where('is_deleted', false)
+            ->cursor()
+            ->each(function (Invoice $invoice) {
+
+
+                $line_items = $invoice->line_items;
+
+                foreach ($line_items as $key => $item) {
+
+                    if(property_exists($item, 'product_cost') && $item->product_cost == 0 && $product = Product::where('company_id', $invoice->company_id)->where('product_key', $item->product_key)->where('cost', '>', 0)->first()) {
+                        $line_items[$key]->product_cost = $product->cost;
+                    }
+                }
+
+                $invoice->line_items = $line_items;
+                $invoice->saveQuietly();
+
+            });
+
+
+        $i = $i->fresh();
+        $line_items = $i->line_items;
+
+        $this->assertEquals(10, $line_items[0]->product_cost);
+
+
+    }
+
     public function testSetTaxId()
     {
         $p = Product::factory()->create([
diff --git a/tests/Unit/CurrencyApiTest.php b/tests/Unit/CurrencyApiTest.php
index 153e566b25df..5db10d26ef9f 100644
--- a/tests/Unit/CurrencyApiTest.php
+++ b/tests/Unit/CurrencyApiTest.php
@@ -12,6 +12,7 @@
 namespace Tests\Unit;
 
 use App\Libraries\Currency\Conversion\CurrencyApi;
+use App\Models\Currency;
 use Illuminate\Support\Carbon;
 use Tests\TestCase;
 
@@ -26,6 +27,21 @@ class CurrencyApiTest extends TestCase
         parent::setUp();
     }
 
+    public function testConversionAudToEur()
+    {
+        $converter = new CurrencyApi();
+
+        $converted_amount = $converter->convert(100, 12, 3);
+
+        $aud_currency = Currency::find(12);
+        $eur_currency = Currency::find(3);
+
+        $converted_synthetic = 100 / ($aud_currency->exchange_rate / $eur_currency->exchange_rate);
+
+        $this->assertEquals(round($converted_synthetic, 2), round($converted_amount, 2));
+        
+    }
+
     public function testCurrencyConversionWorking()
     {
         $converter = new CurrencyApi();