diff --git a/VERSION.txt b/VERSION.txt
index 9ee40d9560..d7896a867f 100644
--- a/VERSION.txt
+++ b/VERSION.txt
@@ -1 +1 @@
-5.1.30
\ No newline at end of file
+5.1.31
\ No newline at end of file
diff --git a/app/Http/Controllers/SubdomainController.php b/app/Http/Controllers/SubdomainController.php
new file mode 100644
index 0000000000..73733e382c
--- /dev/null
+++ b/app/Http/Controllers/SubdomainController.php
@@ -0,0 +1,39 @@
+<?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://opensource.org/licenses/AAL
+ */
+
+namespace App\Http\Controllers;
+
+use App\Libraries\MultiDB;
+
+class SubdomainController extends BaseController
+{
+
+    public function __construct()
+    {
+
+    }
+
+    /**
+     * Display a listing of the resource.
+     *
+     * @return void
+     */
+    public function index()
+    {
+        $subdomain_exists = MultiDB::findAndSetDbByDomain(request()->input('subdomain'));
+
+        if($subdomain_exists)
+            return response()->json(['message' => 'Domain not available'] , 401);
+
+        return response()->json(['message' => 'Domain available'], 200);
+    }
+
+}
diff --git a/app/Http/Livewire/BillingPortalPurchase.php b/app/Http/Livewire/BillingPortalPurchase.php
index b3a5148c7f..bfb35d4697 100644
--- a/app/Http/Livewire/BillingPortalPurchase.php
+++ b/app/Http/Livewire/BillingPortalPurchase.php
@@ -271,6 +271,7 @@ class BillingPortalPurchase extends Component
             ->createInvoice($data)
             ->service()
             ->markSent()
+            ->fillDefaults()
             ->save();
 
         Cache::put($this->hash, [
diff --git a/app/Jobs/RecurringInvoice/SendRecurring.php b/app/Jobs/RecurringInvoice/SendRecurring.php
index 843c722d1d..8dac7d6cfc 100644
--- a/app/Jobs/RecurringInvoice/SendRecurring.php
+++ b/app/Jobs/RecurringInvoice/SendRecurring.php
@@ -63,6 +63,7 @@ class SendRecurring implements ShouldQueue
                            ->markSent()
                            ->applyNumber()
                            ->createInvitations()
+                           ->fillDefaults()
                            ->save();
 
         nlog("Invoice {$invoice->number} created");
diff --git a/app/Mail/Engine/QuoteEmailEngine.php b/app/Mail/Engine/QuoteEmailEngine.php
index 9d85d8b68d..548728bb12 100644
--- a/app/Mail/Engine/QuoteEmailEngine.php
+++ b/app/Mail/Engine/QuoteEmailEngine.php
@@ -11,6 +11,7 @@
 
 namespace App\Mail\Engine;
 
+use App\Models\Account;
 use App\Utils\HtmlEngine;
 use App\Utils\Number;
 
diff --git a/app/Services/BillingSubscription/BillingSubscriptionService.php b/app/Services/BillingSubscription/BillingSubscriptionService.php
index c030678d38..b68a9e7fc1 100644
--- a/app/Services/BillingSubscription/BillingSubscriptionService.php
+++ b/app/Services/BillingSubscription/BillingSubscriptionService.php
@@ -20,12 +20,14 @@ use App\Models\PaymentHash;
 use App\Models\Product;
 use App\Models\SystemLog;
 use App\Repositories\InvoiceRepository;
+use App\Utils\Traits\CleanLineItems;
 use App\Utils\Traits\MakesHash;
 use GuzzleHttp\RequestOptions;
 
 class BillingSubscriptionService
 {
     use MakesHash;
+    use CleanLineItems;
 
     /** @var BillingSubscription */
     private $billing_subscription;
@@ -68,7 +70,7 @@ class BillingSubscriptionService
     {
         $invoice_repo = new InvoiceRepository();
 
-        $data['line_items'] = $this->createLineItems($data);
+        $data['line_items'] = $this->cleanItems($this->createLineItems($data));
 
         /*
         If trial_enabled -> return early
diff --git a/config/ninja.php b/config/ninja.php
index bb8873be61..6119b502a1 100644
--- a/config/ninja.php
+++ b/config/ninja.php
@@ -13,7 +13,7 @@ return [
     'require_https' => env('REQUIRE_HTTPS', true),
     'app_url' => rtrim(env('APP_URL', ''), '/'),
     'app_domain' => env('APP_DOMAIN', ''),
-    'app_version' => '5.1.30',
+    'app_version' => '5.1.31',
     'minimum_client_version' => '5.0.16',
     'terms_version' => '1.0.1',
     'api_secret' => env('API_SECRET', false),
diff --git a/public/assets/packages/material_design_icons_flutter/lib/fonts/materialdesignicons-webfont.ttf b/public/assets/packages/material_design_icons_flutter/lib/fonts/materialdesignicons-webfont.ttf
old mode 100755
new mode 100644
index 55456295b3..761dfaf8a6
Binary files a/public/assets/packages/material_design_icons_flutter/lib/fonts/materialdesignicons-webfont.ttf and b/public/assets/packages/material_design_icons_flutter/lib/fonts/materialdesignicons-webfont.ttf differ
diff --git a/routes/api.php b/routes/api.php
index 26136e5009..7038fa7856 100644
--- a/routes/api.php
+++ b/routes/api.php
@@ -24,6 +24,7 @@ Route::group(['middleware' => ['api_secret_check', 'email_db']], function () {
 });
 
 Route::group(['middleware' => ['api_db', 'token_auth', 'locale'], 'prefix' => 'api/v1', 'as' => 'api.'], function () {
+    Route::post('check_subdomain', 'SubdomainController@index')->name('check_subdomain');
     Route::get('ping', 'PingController@index')->name('ping');
     Route::get('health_check', 'PingController@health')->name('health_check');