diff --git a/public/userarea/validate_export.php b/public/userarea/validate_export.php
index aad2723..ecbd835 100644
--- a/public/userarea/validate_export.php
+++ b/public/userarea/validate_export.php
@@ -88,6 +88,58 @@ $validators[] = function (int $iddatadb, array $ctx): array {
     return [];
 };
 
+// 3. All LIMS-mandatory fields must be filled.
+$validators[] = function (int $iddatadb, array $ctx): array {
+    $record = $ctx['record'] ?? null;
+    if (!$record) {
+        return [];
+    }
+
+    $errors = [];
+
+    // Fixed fields (stored as columns in datadb)
+    foreach (($ctx['requiredFixed'] ?? []) as $key => $label) {
+        $col = $ctx['fixedAliasMap'][$key] ?? null;
+        $val = $col !== null ? ($record[$col] ?? null) : null;
+        if ($val === null || $val === '' || (int) $val === 0) {
+            $errors[] = [
+                'field'   => $key,
+                'message' => $label . ' è obbligatorio.',
+            ];
+        }
+    }
+
+    // Custom fields (values stored in import_data_details, keyed by mapping_id)
+    foreach (($ctx['requiredCustom'] ?? []) as $cf) {
+        $val = $ctx['customValues'][(int) $cf['mapping_id']] ?? null;
+        if ($val === null || trim((string) $val) === '') {
+            $errors[] = [
+                'field'   => 'field_label:' . $cf['field_label'],
+                'message' => rtrim($cf['field_label'], ': ') . ' è obbligatorio.',
+            ];
+        }
+    }
+
+    return $errors;
+};
+
+// Logical fixed_field_key - real datadb column (mirrors imported.php $fixedAliasMap)
+$fixedAliasMap = [
+    'ClienteResponsabile'      => 'cliente_responsabile_id',
+    'ClienteFornitore'         => 'cliente_fornitore_id',
+    'ClienteAnalisi'           => 'clienteAnalisi',
+    'MoltiplicatorePrezzo'     => 'moltiplicatore_prezzo_id',
+    'AnagraficaCertestObject'  => 'anagrafica_certest_object_id',
+    'AnagraficaCertestService' => 'anagrafica_certest_service_id',
+    'ConsegnaRichiesta'        => 'consegna_richiesta',
+];
+
+// Fixed keys NOT enforced by the generic mandatory check above:
+//  - ConsegnaRichiesta: handled by its dedicated validator (also checks the date)
+//  - ClienteFornitore / ClienteAnalisi: nullable placeholders, sent as null on
+//    export and accepted by LIMS.
+$skipRequiredFixed = ['ConsegnaRichiesta', 'ClienteFornitore', 'ClienteAnalisi'];
+
 // ── Main ────────────────────────────────────────────────────────────────────
 
 try {
@@ -104,9 +156,12 @@ try {
     $iddatadbList = array_column($rows, 'iddatadb');
     $placeholders = implode(',', array_fill(0, count($iddatadbList), '?'));
 
-    // Records (datadb) for fixed field validation
+    // Records (datadb) — templateid + fixed-field columns for mandatory validation
     $stmt = $pdo->prepare("
-        SELECT iddatadb, consegna_richiesta
+        SELECT iddatadb, templateid, consegna_richiesta,
+               cliente_responsabile_id, moltiplicatore_prezzo_id,
+               anagrafica_certest_object_id, anagrafica_certest_service_id,
+               cliente_fornitore_id, clienteAnalisi
         FROM datadb
         WHERE iddatadb IN ($placeholders)
     ");
@@ -128,6 +183,62 @@ try {
         $partsInfo[(int)$r['iddatadb']][] = $r;
     }
 
+    // Mandatory-field config per template
+    $templateIds = array_values(array_unique(array_filter(array_map(
+        fn ($r) => (int)($r['templateid'] ?? 0),
+        $recordsInfo
+    ))));
+
+    $requiredFixedByTemplate  = []; // template_id => [ fixed_field_key => label ]
+    $requiredCustomByTemplate = []; // template_id => [ { mapping_id, field_label }, ... ]
+
+    if (!empty($templateIds)) {
+        $tplPlaceholders = implode(',', array_fill(0, count($templateIds), '?'));
+
+        // Required fixed fields (is_required synced from LIMS ObbligatorioWeb)
+        $stmt = $pdo->prepare("
+            SELECT template_id, fixed_field_key
+            FROM template_fixed_mapping
+            WHERE template_id IN ($tplPlaceholders) AND is_required = 1
+        ");
+        $stmt->execute($templateIds);
+        foreach ($stmt->fetchAll(PDO::FETCH_ASSOC) as $r) {
+            $key = $r['fixed_field_key'];
+            if (in_array($key, $skipRequiredFixed, true)) {
+                continue;
+            }
+            $requiredFixedByTemplate[(int)$r['template_id']][$key] = $key;
+        }
+
+        // Required custom fields that are visible in the import grid
+        $stmt = $pdo->prepare("
+            SELECT id AS mapping_id, template_id, field_label
+            FROM template_mapping
+            WHERE template_id IN ($tplPlaceholders)
+              AND is_required = 1
+              AND is_visible_import = 1
+        ");
+        $stmt->execute($templateIds);
+        foreach ($stmt->fetchAll(PDO::FETCH_ASSOC) as $r) {
+            $requiredCustomByTemplate[(int)$r['template_id']][] = [
+                'mapping_id'  => (int)$r['mapping_id'],
+                'field_label' => $r['field_label'],
+            ];
+        }
+    }
+
+    // Custom field values per record (import_data_details.id is the FK to datadb)
+    $stmt = $pdo->prepare("
+        SELECT id AS iddatadb, mapping_id, field_value
+        FROM import_data_details
+        WHERE id IN ($placeholders)
+    ");
+    $stmt->execute($iddatadbList);
+    $customValuesByRecord = []; // iddatadb => [ mapping_id => field_value ]
+    foreach ($stmt->fetchAll(PDO::FETCH_ASSOC) as $r) {
+        $customValuesByRecord[(int)$r['iddatadb']][(int)$r['mapping_id']] = $r['field_value'];
+    }
+
     // ── Run validators per row ──────────────────────────────────────────────
 
     $results = [];
@@ -137,9 +248,15 @@ try {
         $index = $rowInfo['index'];
 
         // Build context for validators
+        $record    = $recordsInfo[$iddatadb] ?? null;
+        $templateId = (int)($record['templateid'] ?? 0);
         $ctx = [
-            'record' => $recordsInfo[$iddatadb] ?? null,
-            'parts'  => $partsInfo[$iddatadb] ?? [],
+            'record'         => $record,
+            'parts'          => $partsInfo[$iddatadb] ?? [],
+            'fixedAliasMap'  => $fixedAliasMap,
+            'requiredFixed'  => $requiredFixedByTemplate[$templateId]  ?? [],
+            'requiredCustom' => $requiredCustomByTemplate[$templateId] ?? [],
+            'customValues'   => $customValuesByRecord[$iddatadb] ?? [],
         ];
 
         $errors = [];