diff --git a/app/Http/Controllers/Auth/ContactRegisterController.php b/app/Http/Controllers/Auth/ContactRegisterController.php
index 71af89c4a5fa..c74ea40c7c99 100644
--- a/app/Http/Controllers/Auth/ContactRegisterController.php
+++ b/app/Http/Controllers/Auth/ContactRegisterController.php
@@ -18,11 +18,13 @@ class ContactRegisterController extends Controller
         $this->middleware(['guest', 'contact.register']);
     }
 
-    public function showRegisterForm(string $company_key)
+    public function showRegisterForm(string $company_key = '')
     {
-        $company = Company::where('company_key', $company_key)->firstOrFail();
+        $key = request()->has('key') ? request('key') : $company_key;
 
-        return render('auth.register', compact(['company']));
+        $company = Company::where('company_key', $key)->firstOrFail();
+
+        return render('auth.register', ['company' => $company]);
     }
 
     public function register(RegisterRequest $request)
diff --git a/app/Http/Middleware/ContactRegister.php b/app/Http/Middleware/ContactRegister.php
index b22ab6ecd75c..33c9549a781a 100644
--- a/app/Http/Middleware/ContactRegister.php
+++ b/app/Http/Middleware/ContactRegister.php
@@ -2,7 +2,9 @@
 
 namespace App\Http\Middleware;
 
+use App\Models\Account;
 use App\Models\Company;
+use App\Utils\Ninja;
 use Closure;
 use Illuminate\Http\Request;
 
@@ -11,35 +13,45 @@ class ContactRegister
     /**
      * Handle an incoming request.
      *
-     * @param  Request  $request
+     * @param Request $request
      * @param Closure $next
      * @return mixed
      */
     public function handle($request, Closure $next)
     {
-        /*
-         * Notes:
-         *
-         * 1. If request supports subdomain (for hosted) check domain and continue request.
-         * 2. If request doesn't support subdomain and doesn' have company_key, abort
-         * 3. firstOrFail() will abort with 404 if company with company_key wasn't found.
-         * 4. Abort if setting isn't enabled.
-         */
-
+        // Resolving based on subdomain. Used in version 5 hosted platform.
         if ($request->subdomain) {
             $company = Company::where('subdomain', $request->subdomain)->firstOrFail();
 
             abort_unless($company->getSetting('enable_client_registration'), 404);
 
+            $request->merge(['key' => $company->company_key]);
+
             return $next($request);
         }
 
-        abort_unless($request->company_key, 404);
+        // For self-hosted platforms with multiple companies, resolving is done using company key
+        // if it doesn't resolve using a domain.
+        if ($request->route()->parameter('company_key') && Ninja::isSelfHost()) {
+            $company = Company::where('company_key', $request->company_key)->firstOrFail();
 
-        $company = Company::where('company_key', $request->company_key)->firstOrFail();
+            abort_unless($company->client_can_register, 404);
 
-        abort_unless($company->client_can_register, 404);
+            return $next($request);
+        }
 
-        return $next($request);
+        // As a fallback for self-hosted, it will use default company in the system
+        // if key isn't provided in the url.
+        if (!$request->route()->parameter('company_key') && Ninja::isSelfHost()) {
+            $company = Account::first()->default_company;
+
+            abort_unless($company->client_can_register, 404);
+
+            $request->merge(['key' => $company->company_key]);
+
+            return $next($request);
+        }
+
+        return abort(404);
     }
 }