diff --git a/declarationtva_view.php b/declarationtva_view.php
index 2c326d4..4ca0b31 100644
--- a/declarationtva_view.php
+++ b/declarationtva_view.php
@@ -479,7 +479,7 @@ if ($declarationtva->status == 'draft') {
 } elseif ($declarationtva->status == 'validated') {
     print '<a href="' . $_SERVER['PHP_SELF'] . '?id=' . $id . '&action=submit" class="butAction">' . $langs->trans("Submit") . '</a> ';
     // Add unvalidate button for testing
-    print '<a href="' . $_SERVER['PHP_SELF'] . '?id=' . $id . '&action=unvalidate&token=' . newToken() . '" class="butAction" style="background-color: #dc3545;" onclick="return confirm(\'' . $langs->trans("ConfirmUnvalidate") . '\')">' . $langs->trans("Unvalidate") . '</a> ';
+    print '<a href="#" onclick="confirmUnvalidation(' . $id . '); return false;" class="butAction" style="background-color: #dc3545;">' . $langs->trans("Unvalidate") . '</a> ';
 }
 
 print '<a href="declarationtvaindex.php" class="butAction">' . $langs->trans("BackToList") . '</a>';
@@ -651,6 +651,77 @@ function proceedValidation(declarationId) {
     // Redirect to validation action
     window.location.href = "' . $_SERVER['PHP_SELF'] . '?id=" + declarationId + "&action=validate&token=' . newToken() . '";
 }
+
+function confirmUnvalidation(declarationId) {
+    // Create a proper Dolibarr-style modal dialog for unvalidation
+    var dialog = document.createElement("div");
+    dialog.id = "unvalidationModal";
+    dialog.style.cssText = "position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0,0,0,0.6); z-index: 10000; display: flex; align-items: center; justify-content: center; font-family: Arial, sans-serif;";
+    
+    var dialogContent = document.createElement("div");
+    dialogContent.style.cssText = "background: white; border-radius: 8px; box-shadow: 0 10px 30px rgba(0,0,0,0.3); max-width: 500px; width: 90%; max-height: 90%; overflow: hidden;";
+    
+    // Header
+    var header = document.createElement("div");
+    header.style.cssText = "background: #f8f9fa; padding: 20px; border-bottom: 1px solid #dee2e6; display: flex; align-items: center;";
+    header.innerHTML = `
+        <div style="flex: 1;">
+            <h3 style="margin: 0; color: #495057; font-size: 18px; font-weight: 600;">' . $langs->trans("ConfirmUnvalidate") . '</h3>
+        </div>
+        <button onclick="closeUnvalidationModal()" style="background: none; border: none; font-size: 24px; color: #6c757d; cursor: pointer; padding: 0; width: 30px; height: 30px; display: flex; align-items: center; justify-content: center;">&times;</button>
+    `;
+    
+    // Body
+    var body = document.createElement("div");
+    body.style.cssText = "padding: 20px;";
+    body.innerHTML = `
+        <div style="display: flex; align-items: flex-start; margin-bottom: 20px;">
+            <div style="background: #f8d7da; border: 1px solid #f5c6cb; border-radius: 50%; width: 40px; height: 40px; display: flex; align-items: center; justify-content: center; margin-right: 15px; flex-shrink: 0;">
+                <span style="color: #721c24; font-size: 18px; font-weight: bold;">!</span>
+            </div>
+            <div style="flex: 1;">
+                <p style="margin: 0; color: #495057; line-height: 1.5; font-size: 14px;">' . $langs->trans("UnvalidationConfirmationMessage") . '</p>
+            </div>
+        </div>
+    `;
+    
+    // Footer
+    var footer = document.createElement("div");
+    footer.style.cssText = "background: #f8f9fa; padding: 15px 20px; border-top: 1px solid #dee2e6; display: flex; justify-content: flex-end; gap: 10px;";
+    footer.innerHTML = `
+        <button onclick="closeUnvalidationModal()" style="background: #6c757d; color: white; border: none; padding: 8px 16px; border-radius: 4px; cursor: pointer; font-size: 14px; font-weight: 500;">
+            ' . $langs->trans("Cancel") . '
+        </button>
+        <button onclick="proceedUnvalidation(' . $id . ')" style="background: #dc3545; color: white; border: none; padding: 8px 16px; border-radius: 4px; cursor: pointer; font-size: 14px; font-weight: 500;">
+            ' . $langs->trans("YesUnvalidate") . '
+        </button>
+    `;
+    
+    dialogContent.appendChild(header);
+    dialogContent.appendChild(body);
+    dialogContent.appendChild(footer);
+    dialog.appendChild(dialogContent);
+    document.body.appendChild(dialog);
+    
+    // Add escape key handler
+    document.addEventListener("keydown", function(e) {
+        if (e.key === "Escape") {
+            closeUnvalidationModal();
+        }
+    });
+}
+
+function closeUnvalidationModal() {
+    var modal = document.getElementById("unvalidationModal");
+    if (modal) {
+        modal.remove();
+    }
+}
+
+function proceedUnvalidation(declarationId) {
+    // Redirect to unvalidation action
+    window.location.href = "' . $_SERVER['PHP_SELF'] . '?id=" + declarationId + "&action=unvalidate&token=' . newToken() . '";
+}
 </script>';
 
 // Print footer
diff --git a/langs/en_US/declarationtva.lang b/langs/en_US/declarationtva.lang
index c393e2d..84f2387 100644
--- a/langs/en_US/declarationtva.lang
+++ b/langs/en_US/declarationtva.lang
@@ -513,3 +513,5 @@ DraftDeclaration = Draft Declaration
 ValidatedPDFAvailable = Validated PDF Available
 NoDocument = No Document
 DownloadPDF = Download PDF
+UnvalidationConfirmationMessage = Are you sure you want to unvalidate this declaration? This action will revert the declaration to draft status and remove the generated PDF.
+YesUnvalidate = Yes, unvalidate
diff --git a/langs/fr_FR/declarationtva.lang b/langs/fr_FR/declarationtva.lang
index d4dfb02..785af87 100644
--- a/langs/fr_FR/declarationtva.lang
+++ b/langs/fr_FR/declarationtva.lang
@@ -485,3 +485,5 @@ DraftDeclaration = Déclaration brouillon
 ValidatedPDFAvailable = PDF validé disponible
 NoDocument = Aucun document
 DownloadPDF = Télécharger le PDF
+UnvalidationConfirmationMessage = Êtes-vous sûr de vouloir annuler la validation de cette déclaration ? Cette action remettra la déclaration en mode brouillon et supprimera le PDF généré.
+YesUnvalidate = Oui, annuler la validation