diff --git a/app/Http/Requests/Client/ClientStoreRequest.php b/app/Http/Requests/Client/ClientStoreRequest.php
index b53e45b..09aa304 100644
--- a/app/Http/Requests/Client/ClientStoreRequest.php
+++ b/app/Http/Requests/Client/ClientStoreRequest.php
@@ -96,6 +96,7 @@ public function rules(): array
             // 기타
             'memo' => 'nullable|string',
             'is_active' => 'nullable|boolean',
+            'is_overdue' => 'nullable|boolean',
         ];
     }
 }
diff --git a/app/Http/Requests/Client/ClientUpdateRequest.php b/app/Http/Requests/Client/ClientUpdateRequest.php
index 5995bdb..98c90ed 100644
--- a/app/Http/Requests/Client/ClientUpdateRequest.php
+++ b/app/Http/Requests/Client/ClientUpdateRequest.php
@@ -96,6 +96,7 @@ public function rules(): array
             // 기타
             'memo' => 'nullable|string',
             'is_active' => 'nullable|boolean',
+            'is_overdue' => 'nullable|boolean',
         ];
     }
 }
diff --git a/app/Services/ClientService.php b/app/Services/ClientService.php
index e3f16da..6f44428 100644
--- a/app/Services/ClientService.php
+++ b/app/Services/ClientService.php
@@ -70,13 +70,24 @@ public function index(array $params)
                 ->select('client_id', DB::raw('SUM(debt_amount) as total_bad_debt'))
                 ->pluck('total_bad_debt', 'client_id');
 
+            // 활성 악성채권이 있는 거래처 ID 목록 (금액과 무관하게 레코드 존재 여부)
+            $clientsWithBadDebt = BadDebt::where('tenant_id', $tenantId)
+                ->whereIn('client_id', $clientIds)
+                ->whereIn('status', [BadDebt::STATUS_COLLECTING, BadDebt::STATUS_LEGAL_ACTION])
+                ->where('is_active', true)
+                ->whereNull('deleted_at')
+                ->distinct()
+                ->pluck('client_id')
+                ->flip()
+                ->toArray();
+
             // 각 거래처에 미수금/악성채권 정보 추가
-            $paginator->getCollection()->transform(function ($client) use ($salesByClient, $depositsByClient, $badDebtsByClient) {
+            $paginator->getCollection()->transform(function ($client) use ($salesByClient, $depositsByClient, $badDebtsByClient, $clientsWithBadDebt) {
                 $totalSales = $salesByClient[$client->id] ?? 0;
                 $totalDeposits = $depositsByClient[$client->id] ?? 0;
                 $client->outstanding_amount = max(0, $totalSales - $totalDeposits);
                 $client->bad_debt_total = $badDebtsByClient[$client->id] ?? 0;
-                $client->has_bad_debt = ($badDebtsByClient[$client->id] ?? 0) > 0;
+                $client->has_bad_debt = isset($clientsWithBadDebt[$client->id]);
 
                 return $client;
             });
@@ -108,15 +119,14 @@ public function show(int $id)
         $client->outstanding_amount = max(0, $totalSales - $totalDeposits);
 
         // 악성채권 정보
-        $badDebtTotal = BadDebt::where('tenant_id', $tenantId)
+        $activeBadDebtQuery = BadDebt::where('tenant_id', $tenantId)
             ->where('client_id', $id)
             ->whereIn('status', [BadDebt::STATUS_COLLECTING, BadDebt::STATUS_LEGAL_ACTION])
             ->where('is_active', true)
-            ->whereNull('deleted_at')
-            ->sum('debt_amount');
+            ->whereNull('deleted_at');
 
-        $client->bad_debt_total = $badDebtTotal;
-        $client->has_bad_debt = $badDebtTotal > 0;
+        $client->bad_debt_total = (clone $activeBadDebtQuery)->sum('debt_amount');
+        $client->has_bad_debt = (clone $activeBadDebtQuery)->exists();
 
         return $client;
     }
@@ -173,6 +183,7 @@ private function generateClientCode(int $tenantId): string
     public function update(int $id, array $data)
     {
         $tenantId = $this->tenantId();
+        $userId = $this->apiUserId();
 
         $client = Client::where('tenant_id', $tenantId)->find($id);
         if (! $client) {
@@ -182,11 +193,58 @@ public function update(int $id, array $data)
         // client_code 변경 불가 (프론트에서 보내도 무시)
         unset($data['client_code']);
 
+        // bad_debt 토글 처리 (bad_debts 테이블과 연동)
+        $badDebtToggle = $data['bad_debt'] ?? null;
+        unset($data['bad_debt']); // Client 모델에는 bad_debt 컬럼이 없으므로 제거
+
         $client->update($data);
 
+        // bad_debt 토글이 명시적으로 전달된 경우에만 처리
+        if ($badDebtToggle !== null) {
+            $this->syncBadDebtStatus($client, (bool) $badDebtToggle, $userId);
+        }
+
         return $client->refresh();
     }
 
+    /**
+     * 악성채권 상태 동기화
+     * 프론트엔드의 bad_debt 토글에 따라 bad_debts 테이블 연동
+     */
+    private function syncBadDebtStatus(Client $client, bool $hasBadDebt, ?int $userId): void
+    {
+        $tenantId = $client->tenant_id;
+
+        // 현재 활성 악성채권 조회
+        $activeBadDebt = BadDebt::where('tenant_id', $tenantId)
+            ->where('client_id', $client->id)
+            ->where('is_active', true)
+            ->whereIn('status', [BadDebt::STATUS_COLLECTING, BadDebt::STATUS_LEGAL_ACTION])
+            ->first();
+
+        if ($hasBadDebt && ! $activeBadDebt) {
+            // 악성채권 활성화: 새 레코드 생성
+            BadDebt::create([
+                'tenant_id' => $tenantId,
+                'client_id' => $client->id,
+                'debt_amount' => $client->outstanding_balance ?? 0,
+                'status' => BadDebt::STATUS_COLLECTING,
+                'overdue_days' => 0,
+                'occurred_at' => now(),
+                'is_active' => true,
+                'created_by' => $userId,
+            ]);
+        } elseif (! $hasBadDebt && $activeBadDebt) {
+            // 악성채권 비활성화: 기존 레코드 종료 처리
+            $activeBadDebt->update([
+                'is_active' => false,
+                'status' => BadDebt::STATUS_RECOVERED,
+                'closed_at' => now(),
+                'updated_by' => $userId,
+            ]);
+        }
+    }
+
     /** 삭제 */
     public function destroy(int $id)
     {