diff --git a/index.php b/index.php
index 9e11d48..4121bdf 100644
--- a/index.php
+++ b/index.php
@@ -328,11 +328,12 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
             $items = json_decode($_POST['items'] ?? '[]', true);
             
             // Fetch settings
-            $settings_res = $db->query("SELECT * FROM settings WHERE `key` IN ('loyalty_enabled', 'loyalty_points_per_unit')")->fetchAll(PDO::FETCH_ASSOC);
+            $settings_res = $db->query("SELECT * FROM settings WHERE `key` IN ('loyalty_enabled', 'loyalty_points_per_unit', 'allow_zero_stock_sell')")->fetchAll(PDO::FETCH_ASSOC);
             $app_settings = [];
             foreach ($settings_res as $s) $app_settings[$s['key']] = $s['value'];
             $loyalty_enabled = ($app_settings['loyalty_enabled'] ?? '0') === '1';
             $points_per_unit = (float)($app_settings['loyalty_points_per_unit'] ?? 1);
+            $allow_zero_stock = ($app_settings['allow_zero_stock_sell'] ?? '0') === '1';
 
             if (empty($items)) {
                 throw new Exception("Cart is empty");
@@ -405,9 +406,17 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
                 $price = (float)$item['price'];
                 $subtotal = $qty * $price;
 
-                $stmtVat = $db->prepare("SELECT vat_rate FROM stock_items WHERE id = ?");
-                $stmtVat->execute([$item['id']]);
-                $vat_rate = (float)$stmtVat->fetchColumn();
+                $stmtItem = $db->prepare("SELECT vat_rate, stock_quantity, name_en FROM stock_items WHERE id = ?");
+                $stmtItem->execute([$item['id']]);
+                $item_info = $stmtItem->fetch(PDO::FETCH_ASSOC);
+                $vat_rate = (float)($item_info['vat_rate'] ?? 0);
+                $stock_qty = (float)($item_info['stock_quantity'] ?? 0);
+
+                if (!$allow_zero_stock && ($qty > $stock_qty)) {
+                    throw new Exception("Insufficient stock for item: " . ($item_info['name_en'] ?? 'Unknown'));
+                }
+
+                $item_vat = $subtotal * ($vat_rate / 100);
                 $item_vat = $subtotal * ($vat_rate / 100);
                 $total_vat += $item_vat;
 
@@ -755,6 +764,9 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
             $db = db();
             $db->beginTransaction();
             try {
+                // Fetch settings
+                $allow_zero_stock = $db->query("SELECT `value` FROM settings WHERE `key` = 'allow_zero_stock_sell'")->fetchColumn() === '1';
+
                 $subtotal = 0;
                 $total_vat = 0;
                 
@@ -763,10 +775,19 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
                     $qty = (float)$quantities[$index];
                     $price = (float)$prices[$index];
                     
-                    // Fetch vat_rate for this item
-                    $stmtVat = $db->prepare("SELECT vat_rate FROM stock_items WHERE id = ?");
-                    $stmtVat->execute([$item_id]);
-                    $vat_rate = (float)$stmtVat->fetchColumn();
+                    // Fetch item info
+                    $stmtItem = $db->prepare("SELECT vat_rate, stock_quantity, name_en FROM stock_items WHERE id = ?");
+                    $stmtItem->execute([$item_id]);
+                    $item_info = $stmtItem->fetch(PDO::FETCH_ASSOC);
+                    $vat_rate = (float)($item_info['vat_rate'] ?? 0);
+                    $stock_qty = (float)($item_info['stock_quantity'] ?? 0);
+
+                    if ($type === 'sale' && !$allow_zero_stock && ($qty > $stock_qty)) {
+                        throw new Exception("Insufficient stock for item: " . ($item_info['name_en'] ?? 'Unknown'));
+                    }
+                    
+                    $line_total = $qty * $price;
+                    $line_vat = $line_total * ($vat_rate / 100);
                     
                     $line_total = $qty * $price;
                     $line_vat = $line_total * ($vat_rate / 100);
@@ -889,6 +910,9 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
             $db = db();
             $db->beginTransaction();
             try {
+                // Fetch settings
+                $allow_zero_stock = $db->query("SELECT `value` FROM settings WHERE `key` = 'allow_zero_stock_sell'")->fetchColumn() === '1';
+
                 // Get old invoice type and items to revert stock
                 $stmt = $db->prepare("SELECT type, paid_amount FROM invoices WHERE id = ?");
                 $stmt->execute([$invoice_id]);
@@ -921,9 +945,15 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
                     $qty = (float)$quantities[$index];
                     $price = (float)$prices[$index];
                     
-                    $stmtVat = $db->prepare("SELECT vat_rate FROM stock_items WHERE id = ?");
-                    $stmtVat->execute([$item_id]);
-                    $vat_rate = (float)$stmtVat->fetchColumn();
+                    $stmtItem = $db->prepare("SELECT vat_rate, stock_quantity, name_en FROM stock_items WHERE id = ?");
+                    $stmtItem->execute([$item_id]);
+                    $item_info = $stmtItem->fetch(PDO::FETCH_ASSOC);
+                    $vat_rate = (float)($item_info['vat_rate'] ?? 0);
+                    $stock_qty = (float)($item_info['stock_quantity'] ?? 0);
+
+                    if ($type === 'sale' && !$allow_zero_stock && ($qty > $stock_qty)) {
+                        throw new Exception("Insufficient stock for item: " . ($item_info['name_en'] ?? 'Unknown'));
+                    }
                     
                     $line_total = $qty * $price;
                     $line_vat = $line_total * ($vat_rate / 100);
@@ -986,15 +1016,27 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
             $db = db();
             $db->beginTransaction();
             try {
+                $allow_zero_stock = $db->query("SELECT `value` FROM settings WHERE `key` = 'allow_zero_stock_sell'")->fetchColumn() === '1';
+
                 $subtotal = 0;
                 $total_vat = 0;
                 $items_data = [];
                 foreach ($item_ids as $index => $item_id) {
                     $qty = (float)$quantities[$index];
                     $price = (float)$prices[$index];
-                    $stmtVat = $db->prepare("SELECT vat_rate FROM stock_items WHERE id = ?");
-                    $stmtVat->execute([$item_id]);
-                    $vat_rate = (float)$stmtVat->fetchColumn();
+
+                    $stmtItem = $db->prepare("SELECT vat_rate, stock_quantity, name_en FROM stock_items WHERE id = ?");
+                    $stmtItem->execute([$item_id]);
+                    $item_info = $stmtItem->fetch(PDO::FETCH_ASSOC);
+                    $vat_rate = (float)($item_info['vat_rate'] ?? 0);
+                    $stock_qty = (float)($item_info['stock_quantity'] ?? 0);
+
+                    if (!$allow_zero_stock && ($qty > $stock_qty)) {
+                        throw new Exception("Insufficient stock for item: " . ($item_info['name_en'] ?? 'Unknown'));
+                    }
+
+                    $line_total = $qty * $price;
+                    $line_vat = $line_total * ($vat_rate / 100);
                     $line_total = $qty * $price;
                     $line_vat = $line_total * ($vat_rate / 100);
                     $subtotal += $line_total;
@@ -1032,6 +1074,8 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
             $db = db();
             $db->beginTransaction();
             try {
+                $allow_zero_stock = $db->query("SELECT `value` FROM settings WHERE `key` = 'allow_zero_stock_sell'")->fetchColumn() === '1';
+
                 $stmt = $db->prepare("DELETE FROM quotation_items WHERE quotation_id = ?");
                 $stmt->execute([$quotation_id]);
                 $subtotal = 0;
@@ -1040,9 +1084,17 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
                 foreach ($item_ids as $index => $item_id) {
                     $qty = (float)$quantities[$index];
                     $price = (float)$prices[$index];
-                    $stmtVat = $db->prepare("SELECT vat_rate FROM stock_items WHERE id = ?");
-                    $stmtVat->execute([$item_id]);
-                    $vat_rate = (float)$stmtVat->fetchColumn();
+
+                    $stmtItem = $db->prepare("SELECT vat_rate, stock_quantity, name_en FROM stock_items WHERE id = ?");
+                    $stmtItem->execute([$item_id]);
+                    $item_info = $stmtItem->fetch(PDO::FETCH_ASSOC);
+                    $vat_rate = (float)($item_info['vat_rate'] ?? 0);
+                    $stock_qty = (float)($item_info['stock_quantity'] ?? 0);
+
+                    if (!$allow_zero_stock && ($qty > $stock_qty)) {
+                        throw new Exception("Insufficient stock for item: " . ($item_info['name_en'] ?? 'Unknown'));
+                    }
+
                     $line_total = $qty * $price;
                     $line_vat = $line_total * ($vat_rate / 100);
                     $subtotal += $line_total;
@@ -1080,16 +1132,26 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
             $db = db();
             $db->beginTransaction();
             try {
+                $allow_zero_stock = $db->query("SELECT `value` FROM settings WHERE `key` = 'allow_zero_stock_sell'")->fetchColumn() === '1';
+
                 $stmt = $db->prepare("SELECT * FROM quotations WHERE id = ?");
                 $stmt->execute([$quotation_id]);
                 $q = $stmt->fetch();
                 if (!$q) throw new Exception("Quotation not found");
                 if ($q['status'] === 'converted') throw new Exception("Quotation already converted");
 
-                $stmt = $db->prepare("SELECT * FROM quotation_items WHERE quotation_id = ?");
+                $stmt = $db->prepare("SELECT qi.*, si.stock_quantity, si.name_en FROM quotation_items qi JOIN stock_items si ON qi.item_id = si.id WHERE qi.quotation_id = ?");
                 $stmt->execute([$quotation_id]);
                 $items = $stmt->fetchAll();
 
+                if (!$allow_zero_stock) {
+                    foreach ($items as $item) {
+                        if ($item['quantity'] > $item['stock_quantity']) {
+                            throw new Exception("Insufficient stock for item: " . ($item['name_en'] ?? 'Unknown'));
+                        }
+                    }
+                }
+
                 // Create Invoice
                 $stmt = $db->prepare("INSERT INTO invoices (customer_id, invoice_date, type, status, total_amount, vat_amount, total_with_vat, paid_amount) VALUES (?, CURDATE(), 'sale', 'unpaid', ?, ?, ?, 0)");
                 $stmt->execute([$q['customer_id'], $q['total_amount'], $q['vat_amount'], $q['total_with_vat']]);
@@ -3535,10 +3597,21 @@ $projectDescription = $_SERVER['PROJECT_DESCRIPTION'] ?? 'Accounting System';
             echo json_encode($custData);
         ?>,
         add(product) {
+            const allowZeroStock = companySettings.allow_zero_stock_sell === '1';
+            const currentStock = parseFloat(product.stock_quantity) || 0;
+            
             const existing = this.items.find(item => item.id === product.id);
             if (existing) {
+                if (!allowZeroStock && (existing.qty + 1) > currentStock) {
+                    alert('Insufficient stock!');
+                    return;
+                }
                 existing.qty++;
             } else {
+                if (!allowZeroStock && currentStock <= 0) {
+                    alert('Insufficient stock!');
+                    return;
+                }
                 this.items.push({...product, qty: 1});
             }
             this.render();
@@ -3550,6 +3623,14 @@ $projectDescription = $_SERVER['PROJECT_DESCRIPTION'] ?? 'Accounting System';
         updateQty(id, delta) {
             const item = this.items.find(i => i.id === id);
             if (item) {
+                const allowZeroStock = companySettings.allow_zero_stock_sell === '1';
+                const currentStock = parseFloat(item.stock_quantity) || 0;
+                
+                if (delta > 0 && !allowZeroStock && (item.qty + delta) > currentStock) {
+                    alert('Insufficient stock!');
+                    return;
+                }
+
                 item.qty += delta;
                 if (item.qty <= 0) this.remove(id);
                 else this.render();
@@ -6103,7 +6184,14 @@ $projectDescription = $_SERVER['PROJECT_DESCRIPTION'] ?? 'Accounting System';
                     <label class="form-label" data-en="Address" data-ar="العنوان">Address</label>
                     <textarea name="settings[company_address]" class="form-control" rows="3"><?= htmlspecialchars($data['settings']['company_address'] ?? '') ?></textarea>
                 </div>
-                <div class="col-md-4">
+                <div class="col-md-4 mt-3">
+                    <label class="form-label" data-en="Allow Selling Out of Stock" data-ar="السماح بالبيع عند نفاذ المخزون">Allow Selling Out of Stock</label>
+                    <select name="settings[allow_zero_stock_sell]" class="form-select">
+                        <option value="0" <?= ($data['settings']['allow_zero_stock_sell'] ?? '0') === '0' ? 'selected' : '' ?> data-en="Disabled" data-ar="معطل">Disabled</option>
+                        <option value="1" <?= ($data['settings']['allow_zero_stock_sell'] ?? '1') === '1' ? 'selected' : '' ?> data-en="Enabled" data-ar="مفعل">Enabled</option>
+                    </select>
+                </div>
+                <div class="col-md-4 mt-3">
                     <label class="form-label" data-en="Company Logo" data-ar="شعار الشركة">Company Logo</label>
                     <input type="file" name="company_logo" class="form-control" accept="image/*">
                     <?php if (!empty($data['settings']['company_logo'])): ?>
@@ -6900,6 +6988,22 @@ document.addEventListener('DOMContentLoaded', function() {
     function addItemToTable(item, tableBody, searchInput, suggestions, grandTotalEl, subtotalEl, totalVatEl, customData = null) {
         if (suggestions) suggestions.style.display = 'none';
         if (searchInput) searchInput.value = '';
+
+        const allowZeroStock = companySettings.allow_zero_stock_sell === '1';
+        const currentStock = parseFloat(item.stock_quantity) || 0;
+
+        if (invoiceType === 'sale' && !allowZeroStock && !customData) {
+            const existingInTable = Array.from(tableBody.querySelectorAll('.item-row')).find(row => row.querySelector('.item-id-input').value == item.id);
+            let currentQtyInTable = 0;
+            if (existingInTable) {
+                currentQtyInTable = parseFloat(existingInTable.querySelector('.item-qty').value) || 0;
+            }
+            
+            if (currentQtyInTable + 1 > currentStock) {
+                alert('Insufficient stock! Available: ' + currentStock);
+                return;
+            }
+        }
         
         const existingRow = Array.from(tableBody.querySelectorAll('.item-id-input')).find(input => input.value == item.id);
         if (existingRow && !customData) {
@@ -6919,6 +7023,7 @@ document.addEventListener('DOMContentLoaded', function() {
         row.innerHTML = `
             <td>
                 <input type="hidden" name="item_ids[]" class="item-id-input" value="${item.id}">
+                <input type="hidden" class="item-row-stock" value="${item.stock_quantity}">
                 <input type="hidden" class="item-vat-rate" value="${vatRate}">
                 <div><strong>${item.name_en}</strong></div>
                 <div class="small text-muted">${item.name_ar} (${item.sku})</div>
@@ -6958,7 +7063,18 @@ document.addEventListener('DOMContentLoaded', function() {
     }
 
     function attachRowListeners(row, tableBody, grandTotalEl, subtotalEl, totalVatEl) {
-        row.querySelector('.item-qty').addEventListener('input', () => recalculate(tableBody, grandTotalEl, subtotalEl, totalVatEl));
+        row.querySelector('.item-qty').addEventListener('input', function() {
+            const allowZeroStock = companySettings.allow_zero_stock_sell === '1';
+            if (invoiceType === 'sale' && !allowZeroStock) {
+                const stock = parseFloat(row.querySelector('.item-row-stock').value) || 0;
+                const qty = parseFloat(this.value) || 0;
+                if (qty > stock) {
+                    alert('Insufficient stock! Available: ' + stock);
+                    this.value = stock;
+                }
+            }
+            recalculate(tableBody, grandTotalEl, subtotalEl, totalVatEl);
+        });
         row.querySelector('.item-price').addEventListener('input', () => recalculate(tableBody, grandTotalEl, subtotalEl, totalVatEl));
         row.querySelector('.remove-row').addEventListener('click', function() {
             row.remove();