diff --git a/core/class/declarationtva_pdf.class.php b/core/class/declarationtva_pdf.class.php
index b293906..f9a1333 100644
--- a/core/class/declarationtva_pdf.class.php
+++ b/core/class/declarationtva_pdf.class.php
@@ -300,7 +300,7 @@ class DeclarationTVA_PDF
             error_log("DeclarationTVA: No SIRET found in company configuration. Please configure SIRET in Dolibarr company settings.");
         }
         
-        $field_data['company_siret'] = $siret_value;
+        $field_data['company_siret'] = $this->formatSiret($siret_value);
         
         $field_data['company_vat_number'] = $mysoc->tva_intra; // VAT number
         $field_data['declaration_period_start'] = dol_print_date($declaration->start_date, 'day');
@@ -1077,4 +1077,34 @@ class DeclarationTVA_PDF
 
         return '0,00';
     }
+
+    /**
+     * Format SIRET number with special spacing
+     * Adds space between every character, with extra space before last 5 characters
+     *
+     * @param string $siret SIRET number
+     * @return string Formatted SIRET
+     */
+    private function formatSiret($siret)
+    {
+        // Remove any existing spaces or special characters
+        $siret = preg_replace('/[^0-9]/', '', $siret);
+        
+        // If SIRET is not configured or too short, return as is
+        if (empty($siret) || $siret === 'SIRET_NOT_CONFIGURED' || strlen($siret) < 5) {
+            return $siret;
+        }
+        
+        // Split into parts: main part and last 5 characters
+        $main_part = substr($siret, 0, -5);
+        $last_5 = substr($siret, -5);
+        
+        // Add space between every character in main part
+        $formatted_main = implode(' ', str_split($main_part));
+        
+        // Add space between every character in last 5, with extra space before
+        $formatted_last = ' ' . implode(' ', str_split($last_5));
+        
+        return $formatted_main . $formatted_last;
+    }
 }