diff --git a/app/Filters/InvoiceFilters.php b/app/Filters/InvoiceFilters.php
index 4bb25f586..d46a9b058 100644
--- a/app/Filters/InvoiceFilters.php
+++ b/app/Filters/InvoiceFilters.php
@@ -67,7 +67,7 @@ class InvoiceFilters extends QueryFilters
         return $this->builder;
     }
 
-    public function number(string $number) :Builder
+    public function number(string $number = '') :Builder
     {
         return $this->builder->where('number', $number);
     }