diff --git a/api/src/Models/WorkingHoursView.php b/api/src/Models/WorkingHoursView.php
index fdfa397..b229ec8 100644
--- a/api/src/Models/WorkingHoursView.php
+++ b/api/src/Models/WorkingHoursView.php
@@ -91,12 +91,13 @@ class WorkingHoursView implements ModelInterface
                   'overtime'          => "string"
     ])] public function jsonSerialize(): array
     {
+        $formatOvertime = (($this->getOvertime()->invert === 1) ? '-' : '') . '%H:%I:%S';
         return [
             'period'            => $this->getPeriod()->format($this->getPeriodDesignation()->getValue()),
             'periodDesignation' => strtolower($this->getPeriodDesignation()->getKey()),
             'workingDays'       => $this->getWorkingDays(),
             'totalHours'        => $this->getTotalHours()->format('%H:%I:%S'),
-            'overtime'          => $this->getOvertime()->format('%H:%I:%S')
+            'overtime'          => $this->getOvertime()->format($formatOvertime)
         ];
     }
 }
\ No newline at end of file