diff --git a/app/Services/PembiayaanOnline/PembiayaanOnlineService.php b/app/Services/PembiayaanOnline/PembiayaanOnlineService.php
index 31fde74..b57e7e4 100644
--- a/app/Services/PembiayaanOnline/PembiayaanOnlineService.php
+++ b/app/Services/PembiayaanOnline/PembiayaanOnlineService.php
@@ -593,20 +593,14 @@ class PembiayaanOnlineService
                     }
                 }
 
-                $batchNo = $this->nextBatchNo($mysql, $kodcaw, $tarikh, $slot);
-                $jumlah = round((float) $lines->sum('pinjaman'), 2);
-
-                $batch = BatchPembiayaanOnline::on($mysql)->create([
-                    'batch_no' => $batchNo,
-                    'kodcaw' => $kodcaw,
-                    'tarikh' => $tarikh,
-                    'slot' => $slot,
-                    'bilangan' => $lines->count(),
-                    'jumlah_keseluruhan' => $jumlah,
-                    'status' => 'SUBMITTED',
-                    'pc_submitted_by' => $pcBy,
-                    'submitted_at' => $now,
-                ]);
+                list($batch, $appended) = $this->findOrCreateSlotBatch(
+                    $mysql,
+                    $kodcaw,
+                    $tarikh,
+                    $slot,
+                    $pcBy,
+                    $now
+                );
 
                 foreach ($lines as $line) {
                     PembiayaanOnline::on($mysql)->where('id', $line->id)->update([
@@ -619,6 +613,14 @@ class PembiayaanOnlineService
                     ]);
                 }
 
+                if ($appended) {
+                    BatchPembiayaanOnline::on($mysql)->where('id', $batch->id)->update([
+                        'submitted_at' => $now,
+                    ]);
+                }
+
+                $batch = $this->refreshBatchStatus($mysql, $batch->id);
+
                 $freshLines = PembiayaanOnline::on($mysql)
                     ->where('batch_id', $batch->id)
                     ->orderBy('id', 'asc')
@@ -626,11 +628,12 @@ class PembiayaanOnlineService
 
                 return [
                     'ok' => true,
-                    'status' => 201,
+                    'status' => $appended ? 200 : 201,
                     'payload' => [
                         'batch' => $batch,
                         'lines' => $freshLines,
                         'slot_info' => $slotInfo,
+                        'appended' => $appended,
                     ],
                 ];
             });
@@ -1535,24 +1538,45 @@ class PembiayaanOnlineService
         ];
     }
 
-    protected function nextBatchNo($mysql, $kodcaw, $tarikh, $slot)
+    /**
+     * One batch per branch / day / slot (B1-001 or B2-001). Later submits append.
+     *
+     * @return array{0:\App\BatchPembiayaanOnline,1:bool} [batch, appended]
+     */
+    protected function findOrCreateSlotBatch($mysql, $kodcaw, $tarikh, $slot, $pcBy, $now)
     {
-        $slotTag = $slot === 'BATCH1' ? 'B1' : 'B2';
-        $ymd = Carbon::parse($tarikh)->format('Ymd');
-        $prefix = strtoupper($kodcaw) . '-PO-' . $ymd . '-' . $slotTag . '-';
-
-        $last = BatchPembiayaanOnline::on($mysql)
+        $batch = BatchPembiayaanOnline::on($mysql)
             ->where('kodcaw', $kodcaw)
             ->where('tarikh', $tarikh)
             ->where('slot', $slot)
-            ->orderBy('id', 'desc')
+            ->orderBy('id', 'asc')
+            ->lockForUpdate()
             ->first();
 
-        $seq = 1;
-        if ($last && preg_match('/-(\d+)$/', $last->batch_no, $m)) {
-            $seq = ((int) $m[1]) + 1;
+        if ($batch) {
+            return [$batch, true];
         }
 
-        return $prefix . str_pad((string) $seq, 3, '0', STR_PAD_LEFT);
+        $batch = BatchPembiayaanOnline::on($mysql)->create([
+            'batch_no' => $this->slotBatchNo($kodcaw, $tarikh, $slot),
+            'kodcaw' => $kodcaw,
+            'tarikh' => $tarikh,
+            'slot' => $slot,
+            'bilangan' => 0,
+            'jumlah_keseluruhan' => 0,
+            'status' => 'SUBMITTED',
+            'pc_submitted_by' => $pcBy,
+            'submitted_at' => $now,
+        ]);
+
+        return [$batch, false];
+    }
+
+    protected function slotBatchNo($kodcaw, $tarikh, $slot)
+    {
+        $slotTag = $slot === 'BATCH1' ? 'B1' : 'B2';
+        $ymd = Carbon::parse($tarikh)->format('Ymd');
+
+        return strtoupper($kodcaw) . '-PO-' . $ymd . '-' . $slotTag . '-001';
     }
 }