diff --git a/app/Http/Controllers/Api/Admin/HR/PayrollController.php b/app/Http/Controllers/Api/Admin/HR/PayrollController.php
index c4aad48b..1d9dd834 100644
--- a/app/Http/Controllers/Api/Admin/HR/PayrollController.php
+++ b/app/Http/Controllers/Api/Admin/HR/PayrollController.php
@@ -91,6 +91,11 @@ public function store(Request $request): JsonResponse
                 'message' => '급여가 등록되었습니다.',
                 'data' => $payroll,
             ], 201);
+        } catch (\InvalidArgumentException $e) {
+            return response()->json([
+                'success' => false,
+                'message' => $e->getMessage(),
+            ], 422);
         } catch (\Throwable $e) {
             report($e);
 
diff --git a/app/Models/HR/PayrollSetting.php b/app/Models/HR/PayrollSetting.php
index 30dba1cc..f2871aa8 100644
--- a/app/Models/HR/PayrollSetting.php
+++ b/app/Models/HR/PayrollSetting.php
@@ -62,7 +62,7 @@ class PayrollSetting extends Model
 
     public function scopeForTenant($query, ?int $tenantId = null)
     {
-        $tenantId = $tenantId ?? session('selected_tenant_id', 1);
+        $tenantId = $tenantId ?? session('selected_tenant_id') ?? 1;
 
         return $query->where('tenant_id', $tenantId);
     }
@@ -73,7 +73,7 @@ public function scopeForTenant($query, ?int $tenantId = null)
 
     public static function getOrCreate(?int $tenantId = null): self
     {
-        $tenantId = $tenantId ?? session('selected_tenant_id', 1);
+        $tenantId = $tenantId ?? session('selected_tenant_id') ?? 1;
 
         return self::firstOrCreate(
             ['tenant_id' => $tenantId],
diff --git a/app/Services/HR/PayrollService.php b/app/Services/HR/PayrollService.php
index dda7f4ac..c145badd 100644
--- a/app/Services/HR/PayrollService.php
+++ b/app/Services/HR/PayrollService.php
@@ -136,6 +136,19 @@ public function storePayroll(array $data): Payroll
     {
         $tenantId = session('selected_tenant_id', 1);
 
+        // 동일 대상/기간 중복 체크
+        $exists = Payroll::where('tenant_id', $tenantId)
+            ->where('user_id', $data['user_id'])
+            ->where('pay_year', $data['pay_year'])
+            ->where('pay_month', $data['pay_month'])
+            ->exists();
+
+        if ($exists) {
+            throw new \InvalidArgumentException(
+                "해당 직원의 {$data['pay_year']}년 {$data['pay_month']}월 급여가 이미 등록되어 있습니다."
+            );
+        }
+
         return DB::transaction(function () use ($data, $tenantId) {
             $calculated = $this->calculateAmounts($data);