diff --git a/pages/sales_purchases_logic.php b/pages/sales_purchases_logic.php
index e47a240..72b9ab1 100644
--- a/pages/sales_purchases_logic.php
+++ b/pages/sales_purchases_logic.php
@@ -1,5 +1,27 @@
 <?php
 // Shared Sales/Purchases data loading extracted from index.php to reduce risk when editing this module.
+        $requestedLimit = isset($limit) ? (int)$limit : (isset($_GET['limit']) ? (int)$_GET['limit'] : 20);
+        if ($requestedLimit < 1) {
+            if (function_exists('runtime_debug_mark')) {
+                runtime_debug_mark('page:sales_purchases_limit_fallback', [
+                    'page' => (string)($page ?? ''),
+                    'requested_limit' => isset($_GET['limit']) ? (string)$_GET['limit'] : 'unset',
+                    'applied_limit' => 20,
+                ]);
+            }
+            if (function_exists('app_debug_file_log')) {
+                app_debug_file_log(
+                    'runtime_debug.log',
+                    date('Y-m-d H:i:s') . " [sales_purchases_limit_fallback] page=" . (string)($page ?? '')
+                    . " requested_limit=" . (isset($_GET['limit']) ? (string)$_GET['limit'] : 'unset')
+                    . " applied_limit=20"
+                );
+            }
+        }
+        $limit = min(500, max(5, $requestedLimit > 0 ? $requestedLimit : 20));
+        $page_num = isset($page_num) ? max(1, (int)$page_num) : (isset($_GET['p']) ? max(1, (int)$_GET['p']) : 1);
+        $offset = ($page_num - 1) * $limit;
+
         $type = ($page === 'sales') ? 'sale' : 'purchase';
         $table = ($type === 'purchase') ? 'purchases' : 'invoices';
         $cust_supplier_col = ($type === 'purchase') ? 'supplier_id' : 'customer_id';